Nervous and Endocrine Systems (OLI)



Now that we have considered how individual neurons operate and the roles of the different brain areas, it is time to ask how the body manages to “put it all together.” 
How do the complex activities in the various parts of the brain, the simple all-or-nothing firings of billions of interconnected neurons, and the various chemical systems within the body, work together to allow the body to respond to the social environment and engage in everyday behaviors? In this section, we will see that the complexities of human behavior are accomplished through the joint actions of electrical and chemical processes in the nervous system and the endocrine system.

The Central Nervous System

The nervous system, the electrical information highway of the body, is made up of nerves—bundles of interconnected neurons that fire in synchrony to carry messages. The central nervous system (CNS) , made up of the brain and spinal cord, is the major controller of the body’s functions, charged with interpreting sensory information and responding to it with its own directives. The CNS interprets information coming in from the senses, formulates an appropriate reaction, and sends responses to the appropriate system to respond accordingly. Everything we see, hear, smell, touch, and taste is conveyed to us from our sensory organs as neural impulses, and each of the commands that the brain sends to the body, both consciously and unconsciously, travels through this system as well.


Nerves are differentiated according to their function. A sensory neuron carries information from the sensory receptors, whereas a motor neuron transmits information to the muscles and glands. An interneuron, which is by far the most common type of neuron, is located primarily within the CNS and is responsible for communicating among the neurons. Interneurons allow the brain to combine the multiple sources of available information to create a coherent picture of the sensory information being conveyed.

The spinal cord is the long, thin, tubular bundle of nerves and supporting cells that extends down from the brain. It is the central pathway of information for the body. Within the spinal cord, ascending tracts of sensory neurons relay sensory information from the sense organs to the brain while descending tracts of motor neurons relay motor commands back to the body. When a quicker-than-usual response is required, the spinal cord can do its own processing, bypassing the brain altogether. A reflex is an involuntary and nearly instantaneous movement in response to a stimulus. Reflexes are triggered when sensory information is powerful enough to reach a given threshold and the interneurons in the spinal cord act to send a message back through the motor neurons without relaying the information to the brain, as shown in the following figure. When you touch a hot stove and immediately pull your hand back, or when you fumble your cell phone and instinctively reach to catch it before it falls, reflexes in your spinal cord order the appropriate responses before your brain even knows what is happening.

The central nervous system can interpret signals from sensory neurons and respond to them extremely quickly via the motor neurons without any need for the brain to be involved. These quick responses, known as reflexes, can reduce the damage that we might experience as a result of, for instance, touching a hot stove.
The central nervous system can interpret signals from sensory neurons and respond to them extremely quickly via the motor neurons without any need for the brain to be involved. These quick responses, known as reflexes, can reduce the damage that we might experience as a result of, for instance, touching a hot stove.

Did I get this

The nervous system can best be described as __________________.
  • the brain and spinal cord of the body
  • the brain
  • the central nervous system
  • the electrical information highway of nerves throughout the body
The nervous system includes all the nerves in your body. It is like a highway in that it allows us to send or transport electrical signals long distances as well as very short distances.


The central nervous system is _______________________.
  • the nerves
  • the spinal cord
  • the brain
  • the brain and the spinal cord
The brain and spinal cord together make up the central nervous system. They serve the primary command and control functions for the body. Other parts of the nervous system carry messages and activate muscles and glands in response to commands from the central nervous system.


Which type of neuron carries information to the muscles and glands of the body?
interneuron OR sensory neuron OR motor neuron OR neurotransmitter
Motor neurons carry messages from the brain and spinal cord to the body, including muscles and glands. The term motor refers to movement, so these are the neurons that activate muscles that allow you to move.


The difference in the function of the nervous system and the central nervous system is that:
  • the nervous system is the major controller of the body's functions
  • the nervous system primarily consists of interneurons
  • the nervous system is the major controller of the body's functions
  • the nervous system is the electrical information highway of the body
The difference in the function of the nervous system and the central nervous system is that the central nervous system is the major controller of the body’s functions. The nervous system is the electrical information highway consisting of nerves that transmit messages from the central nervous system to various parts of the body.


Reflexes are:
  • quick and involuntary movements initialed by interneurons in the brain in response to strong stimuli
  • quick and involuntary movements initialed by interneurons in the spinal cord in response to strong stimuli
  • voluntary reactions to external stimuli received from sensory receptors
  • slow and involuntary movements initiated by nerves in the muscles in response to strong stimuli
When a strong stimulus, such as a hot surface, sends signals down our sensory nerves, interneurons in the spinal cord can initiate a very fast, automatic response—movement of the part of the body touching the hot surface away from the source of pain. Because the signals for a reflex do not need to go all the way to the brain, the reflex can quickly prevent injury that might occur if longer transmission time and more complex processing took place. 

The Peripheral Nervous System

If the central nervous system is the command center of the body, the peripheral nervous system (PNS) represents the front line. The PNS links the CNS to the body’s sense receptors, muscles, and glands. As you can see in the following figure, the PNS is divided into two subsystems, one controlling internal responses and one controlling external responses.

The Functional Divisions of the Nervous System
The autonomic nervous system (ANS) is the division of the PNS that governs the internal activities of the human body, including heart rate, breathing, digestion, salivation, perspiration, urination, and sexual arousal. Many of the actions of the ANS, such as heart rate and digestion, are automatic and out of our conscious control, but others, such as breathing and sexual activity, can be controlled and influenced by conscious processes.

The somatic nervous system (SNS) is the division of the PNS that controls the external aspects of the body, including the skeletal muscles, skin, and sense organs. The somatic nervous system consists primarily of motor nerves responsible for sending brain signals for muscle contraction.

The autonomic nervous system itself can be further subdivided into the sympathetic and parasympathetic systems (see figure below). The sympathetic division of the ANS is involved in preparing the body for rapid action in response to stress from threats or emergencies by activating the organs and glands in the endocrine system. When the sympathetic nervous system recognizes danger or a threat, the heart beats faster, breathing accelerates, and lungs and bronchial tubes expand. These physiological responses increase the amount of oxygen to the brain and muscles to prepare your body for defense. In other sympathetic nervous system responses, your pupils dilate to increase your field of vision, salivation stops and your mouth becomes dry, digestion stops in your stomach and intestines, and you begin to sweat due to your body’s use of more energy and heat. These bodily changes collectively represent the fight-or-flight response, which prepares you to either fight or flee from a perceived danger.

The parasympathetic division of the ANS tends to calm the body by slowing the heart and breathing and by allowing the body to recover from the activities that the sympathetic system causes. The parasympathetic nervous system acts more slowly than the sympathetic nervous system as it calms the activated organs and glands of the endocrine system, eventually returning your body to a normal state, called homeostasis.

The autonomic nervous system has two divisions: The sympathetic division acts the energize the body, preparing it for action. The parasympathetic division acts to calm the body, allowing it to rest.
The autonomic nervous system has two divisions: The sympathetic division acts the energize the body, preparing it for action. The parasympathetic division acts to calm the body, allowing it to rest.
Our everyday activities are also controlled by the interaction between the sympathetic and parasympathetic nervous systems. For example, when we get out of bed in the morning, we would experience a sharp drop in blood pressure if it were not for the action of the sympathetic system, which automatically increases blood flow through the body. Similarly, after we eat a big meal, the parasympathetic system automatically sends more blood to the stomach and intestines, allowing us to efficiently digest the food. And perhaps you’ve had the experience of not being at all hungry before a stressful event, such as a sports game or an exam (when the sympathetic division was primarily in action), but suddenly finding yourself starved afterward, as the parasympathetic system takes over. The two systems work together to maintain vital bodily functions, resulting in homeostasis, the natural balance in the body’s systems.

As you have seen, the nervous system is divided structurally into the central nervous system and the peripheral nervous system. The PNS is further divided into subdivisions, each having a particular function in the nervous system to help regulate the body. In the following activity, you will learn the function of each of the nervous system divisions by matching a specific descriptive function with each structure.




Did I get this

The two main divisions of the nervous system are the ____________.
  • central nervous system and peripheral nervous systen
  • brain and spinal cord
  • somatic and autonomic nervous system
  • spinal and peripheral nervous system
The two main divisions of the nervous system are the central nervous system (CNS) composed of the brain and spinal cord and the peripheral nervous system (PNS) composed of the autonomic nervous system and the somatic nervous system.


The functions of the two key components of the peripheral nervous system are to control:
  • external activities such as muscles, skin, and sense organs and regulate internal activities such as breating and heart rate
  • internal activities such as breating and heart rate and transmit information to the CNS
  • external activities such as muscles, skin, and sense organs and bridge the brain wih the spinal cord
  • external aspects of the body and maintain homeostasis
The functions of the two key components of the peripheral nervous system are to control external activities such as muscles, skin, and sense organs (somatic nervous system) and regulate internal activities such as breathing and heart rate (autonomic nervous system).


The two branches or divisions of the autonomic nervous system are:
  • sympathetic and parasympathetic
  • somatic and peripheral
  • symphatetic and peripheral
  • parasymphatetic and somatic
The two branches or divisions of the autonomic nervous system are the sympathetic and the parasympathetic nervous systems. 


The system that communicates sensory and motor information is called the ________________ nervous system.
somatic OR symphatetic OR parasymphatetic OR autonomic
The somatic nervous system, a subdivision of the peripheral system, controls all external sensory and motor responses of the skeletal muscles, skin, and sense organs.


The part of the nervous system that prepares the body to respond to threatening events is the ____________ division, and the part that helps the body to maintain a normal state of balance is the _____________ division.
  • sympathetic ; parasympathetic
  • autonomic ; parasymphatetic
  • symphatetic ; somatic
  • parasymphatetic ; sympathetic
The sympathetic division prepares the body to respond to threatening events that cause stress, and the parasympathetic division helps the body to maintain a normal state of balance or calmness.


Physiological changes such as increased heart rate, accelerated breathing, dry mouth, and perspiration that occur in response to perceived threats or danger are called ______________.
  • homeostasis
  • fight-or-flight response
  • fight response
  • protective sympathetic response
These types of physiological changes in response to stressful events are collectively called the fight-or-flight response because the body’s natural tendency is to either fight the perceived threat or danger or to flee from it. 

The Endocrine System

The nervous system is designed to protect us from danger through its interpretation of and reactions to stimuli. But a primary function of the sympathetic and parasympathetic nervous systems is to interact with the endocrine system, which secretes chemical messengers called hormones that influence our emotions and behaviors.

The Major Glands of the Endocrine System (male shown on the left and female on the right).
The Major Glands of the Endocrine System. Male shown on left and female on right.
The endocrine system is made up of glands, which are groups of cells that secrete hormones into the bloodstream. When the hormones released by a gland arrive at receptor tissues or other glands, these receiving receptors may trigger the release of other hormones, resulting in a complex chemical chain reaction. The endocrine system works together with the nervous system to influence many aspects of human behavior, including growth, reproduction, and metabolism. The endocrine system also plays a vital role in emotions. Since the glands in men and women differ, the hormones from each of these glands, the ovaries and testes, explain some of the observed behavioral differences between men and women. The major glands in the endocrine system are shown in the figure above.

The secretion of hormones is regulated by the hypothalamus of the brain. The hypothalamus is the main link between the nervous system and the endocrine system and directs the release of hormones by its interactions with the pituitary gland, which is next to and highly interconnected with the hypothalamus. The pituitary gland, a pea-sized gland, is responsible for controlling the body’s growth, but it also has many other influences that make it of primary importance to regulating behavior. The pituitary secretes hormones that influence our responses to pain as well as hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women. Because the pituitary has such an important influence on other glands, it is sometimes known as the “master gland.”

Other glands in the endocrine system include the pancreas, which secretes hormones designed to keep the body supplied with fuel to produce and maintain stores of energy; and the pineal gland, located in the middle of the brain, which secretes melatonin, a hormone that helps regulate the wake-sleep cycle.

The body has two triangular adrenal glands, one on top of each kidney. The adrenal glands produce hormones that regulate salt and water balance in the body, and they are involved in metabolism, the immune system, and sexual development and function. The most important function of the adrenal glands is to secrete the hormones epinephrine (also known as adrenaline) and norepinephrine (also known as noradrenaline) when we are excited, threatened, or stressed. Epinephrine and norepinephrine stimulate the sympathetic division of the autonomic nervous system, causing increased heart and lung activity, dilation of the pupils, and increases in blood sugar, which give the body a surge of energy to respond to a threat. The activity and role of the adrenal glands in response to stress provides an excellent example of the close relationship and interdependency of the nervous and endocrine systems. A quick-acting nervous system is essential for immediate activation of the adrenal glands, while the endocrine system mobilizes the body for action.

At this point, you can begin to see the important role the hormones play in behavior. But the hormones we reviewed in this section represent only a subset of the many influences that hormones have on our behaviors. In the upcoming units, we consider the important roles that hormones play in many other behaviors, including sleeping, sexual activity, and helping and harming others.



Did I get this

The endocrine system is made up of ___________________.
  • group of cells regulated be the pituitary gland
  • glands that send electrical messages to the nervous system
  • nerves that control the body's functions
  • glands that secrete hormones causing a chemical chain reaction to influence behaviour and emotions
The endocrine system is made up of glands or groups of cells that secrete hormones into the bloodstream. The initial release of hormones causes a chemical chain reaction to influence behavior and emotions.


The gland that serves as the main communication link between the endocrine system and the nervous system is the _____________.
pituitary gland OR pineal gland OR adrenal gland OR hypothalamus
The hypothalamus is the main communication link between the endocrine system and the nervous system. The hypothalamus also directs the release of hormones by its interaction with the pituitary gland.


Which endocrine gland secretes hormones that influence responses to pain and signals the ovaries and testes to make sex hormones?
parathyroid OR pineal OR adrenal OR pituitary
The pituitary gland, sometimes known as the master gland, secretes hormones that influence our pain, body growth, and other important bodily functions, and signal the ovaries and testes to make sex hormones.


The __________ gland helps to supply the body with fuel such as glucose, and the ___________ gland secretes melatonin to help us sleep.
  • pancreas; adrenal
  • pancreas; pineal
  • pineal; pancreas
  • adrenal; parathyroid
The pancreas gland secretes hormones designed to keep the body supplied with fuel, such as glucose, to produce and maintain stores of energy; and the pineal gland secretes melatonin to help regulate the wake-sleep cycle.


The most important function of the adrenal glands is to:
  • produce glucose to fuel the body with energy
  • secrete epinephrine and norepinephrine to protect the body from stress
  • produce hormones that regulate salt and water balance in the body
  • secrete hormones that regulate body growth
The adrenal glands have several functions, such as producing hormones that regulate salt and water balance in the body, metabolism, the immune system, and sexual development and function, but the most important function is the secretion of epinephrine and norepinephrine to protect the body from stress.


Roland has trouble staying asleep and getting a good night’s rest. His doctor prescribes a sleep-aid medication of a synthetic hormone because he suspects that Roland has a chemical imbalance in his __________ gland, which is not producing enough __________.
  • pineal; melatonin
  • pituilary; sopamine
  • hypothalamus; melatonin
  • pineal; acetylcholine
The pineal gland secretes melatonin, a hormone that helps regulate the wake-sleep cycle.

Categories:

Blogger news

Popular Posts

Blogroll

Popular Posts