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Nervous System Study Guide

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What organs and structures make up the nervous system? List several functions of the nervous system.
The nervous system consists primarily of the brain, spinal cord, and nerves. Sense organs, such as the eyes and ears are also components of the nervous system. The major functions of this system are to take in sensory information through the sense organs, process that information through the brain and spinal cord, and to generate motor responses by sending signals to the muscles.
Compare and contrast the central nervous system and peripheral nervous system.
Both the central nervous system and peripheral nervous system are made up of neurons and use the same type of signaling (action potentials, synapses, etc.). The central nervous system consists of the brain and spinal cord. It is responsible for processing and integrating responses. The peripheral nervous system consists of all the nerves outside of the central nervous system. It is responsible for sending sensory information from the sense organs to the central nervous system and sending motor information from the central nervous system to the muscles.
Compare and contrast the following sets of terms.
A) White matter vs. Gray matter
B) Sulci vs. Gyri
C) Dura mater vs. Pia mater
D) Motor cortex vs. Somatosensory cortex
E) Cerebrum vs. Cerebral cortex
F) Thalamus vs. Hypothalamus
A) White matter is white and consists of myelinated axons; gray matter is gray and its neurons lack myelin.
B) Sulci are the grooves in the brains; gyri are the bumps between the grooves
C) Dura mater is the tough, outer covering of the brain and spinal cord; pia mater is a thin layer attached directly to the brain and spinal cord.
D) Both the motor cortex and somatosensory cortex are parts of the cerebral cortex and both are subdivided, with different regions dedicated to specific parts of the body. The motor cortex coordinates motor responses and the somatosensory cortex interprets sensory information.
E) The cerebrum is the largest portion of the human brain and is responsible for most higher-order thinking processes. The cerebral cortex is the thin outer layer of the cerebrum.
F) The thalamus relays sensory information to other parts of the brain. The hypothalamus works with the pituitary gland to coordinate the release of hormones. It's responsible for feeding, fighting, fleeing, and mating. Both structures are part of a region of the brain known as the diencephalon. The thalamus is superior and slightly posterior to the hypothalamus.
What is the function of cerebrospinal fluid? Where is it produced and stored?
The cerebrospinal fluid bathes the brain and spinal cord, forming a protective cushion. It is produced and stored in the ventricles.
Identify the structures indicated in the picture below. For each structure, also state its function.
A) Cerebral hemispheres- most higher order thinking processes
B) Thalamus- relays sensory information to other parts of the brain
C) Hypothalamus- works with the pituitary gland to regulate the release of hormones; controls feeding, fleeing, fighting, and mating
D) Diencephalon- portion of the brain that includes the thalamus and hypothalamus (weak definition, I know- this term is used more when discussing brain development, as the thalamus and hypothalamus develop more or less together)
E) Pituitary gland- regulates the release of hormones
F) Midbrain- part of brainstem
G) Pons- part of brainstem
H) Medulla oblongata- part of brainstem
I) Brainstem- helps regulate basic physiological processes such as breathing rate and heart rate
J) Corpus callosum- connects the two cerebral hemispheres
K) Cerebellum- helps regulate balance, coordination, and posture
L) Spinal cord- relays signals between the brain and peripheral nerves
Phineas Gage was a railroad worker who had a large iron rod blast through his head, severely damaging parts of his brain. Though he survived, his personality was dramatically altered. Do you think it's likely that his brainstem was damaged by the rod? Why or why not?
No. The brainstem is responsible for basic physiological processes. If it had been damaged, he would most likely have died. It is more likely that he damaged his cerebrum or limbic system, as these structures are responsible for controlling personality and mood.
The figure to the right indicates which regions of the primary motor cortex control which parts of our bodies. Explain why such a small amount of the motor cortex is devoted to controlling the thigh (a relatively large part of our bodies), while such a large amount of motor cortex is devoted to controlling the thumb, fingers, and hand (a relatively small part of our bodies).
The hands and fingers have lots of different muscles and are capable of a wide variety of motions. A large amount of brain is needed for this fine motor coordination. The thigh, though large, is only capable of a very small number of movements. It therefore does not need as much brain to control it.
Draw a picture of a neuron. Label the following structures on your diagram, then give their functions.
A) Dendrite
B) Axon
C) Cell body
D) Myelin sheath
E) Node of Ranvier
F) Sodium and potassium channels
G) Synaptic terminal
H) Vesicles containing neurotransmitter
See the diagram we drew in class or your textbook for what your picture should look like. Here are the functions, though.
A) Dendrite- receive signals from neighboring neurons
B) Axon- transmits signal down the length of the neuron
C) Cell body- contains nucleus; "sums" incoming excitatory and inhibitory signals from all the dendrites to determine if a new action potential will be fired
D) Myelin sheath- insulates the axon; increases the speed of the signal
E) Node of Ranvier- gaps in the myelin sheath; this is where action potentials are fired
F) Sodium and potassium channels- allow sodium and potassium (respectively)
to cross the membrane; open in response to a positive charge inside the cell; responsible for generating action potentials
G) Synaptic terminal- region of the neuron right next to a synapse; releases
neurotransmitters to pass the signal on to the next neuron
H) Vesicles containing neurotransmitter- store neurotransmitters;release neurotransmitters when an action potential reaches the synaptic terminal
Contrast motor neurons, sensory neurons, and interneurons in terms of location and function.
All three types of neurons are part of the peripheral nervous system. Motor neurons go from the spinal cord to the muscles and are responsible for signaling the muscles to move. Sensory neurons go from the sense organs to the spinal cord and are responsible for bringing in sensory information. Interneurons are located in the gray matter of the spinal cord. They simply relay a signal from a sensory neuron to a motor neuron. They are important in many types of reflex pathways.
What is the function of the myelin sheath? Explain how its structure enables it to carry out this function.
The myelin sheath increases the speed of transmission of a nerve signal down the length of the axon. It does this by forming an insulating layer around the cell. New action potentials can only be generated at the gaps in the myelin sheath, called nodes of Ranvier. As a result, instead of having dozens of action potentials fired along each region of the axon, only a single action potential at each node of Ranvier is all that is needed to propagate the signal.
What is an action potential? Briefly explain the role of sodium and potassium channels in transmitting these signals down a neuron.
An action potential is simply the movement of ions across the membrane of a cell. When the inside of the neuron is depolarized (that is, when it becomes more positive), both the sodium and potassium channels open. The sodium channels are fast and open first, allowing sodium ions to rush inside the cell. This causes the inside of the cell to become positively charged. The potassium channels are slow and open second, allowing potassium to rush out of the cell. This brings the charge inside the cell back to resting conditions. Since the entry of sodium ions makes the inside of the cell more positive, an action potential triggers the opening of more sodium and potassium channels further down the axon. This is an example of positive feedback. Each action potential triggers another one. In this way, the signal travels all the way down the axon to the synaptic terminal.
An action potential is an electrical signal the travels down the length of a neuron.
A) Explain why an action potential is not able to cross the synapse and continue
to the next neuron.
B) What happens when an action potential reaches the end of a neuron? How is the signal transmitted to the next neuron?
A) An action potential requires the movement of sodium and potassium ions across a membrane. It also requires a difference in charge across the membrane (the inside of the cell needs to be more positive than the outside for an action potential to be fired). Since the synaptic terminal is simply a gap, there is no membrane to facilitate these two functions.

B) When an action potential reaches the end of a neuron, it triggers the release of chemicals called neurotransmitters. These neurotransmitters are released into the synapse, travel to the dendrites of the next cell, and open ion channels on that cell. The opening of these ion channels in the next cell causes the entry or exit of sodium or potassium (or some other ion- it depends on the particular neurotransmitter and cell involved). This movement of ions can then trigger a new action potential in the new cell.

Each dendrite on the post-synaptic neuron receives signals. Some of these signals are excitatory, meaning they increase the likelihood of a new action potential. Others are inhibitory, meaning they decrease the likelihood of a new action potential. These excitatory and inhibitory signals sum up in the cell body to determine if a new action potential will be fired or not.

What happens when an action potential reaches the end of a neuron? How is the signal transmitted to the next neuron?
A) What effect does glutamate have on the frequency of action potentials?
B) What effect does GABA have on the frequency of action potentials?
C) Do all neurotransmitters have the same effect? Explain how you know.
A) Glutamate increases the frequency of action potentials.
B) GABA decreases the frequency of action potentials.
C) No. Both glutamate and GABA have a different effect on the neuron. Different neurotransmitters cause different effects.
Explain how cocaine affects the synapse. What are the long-term effects of cocaine use?
Cocaine prevents the neurotransmitters that make you feel happy (dopamine) from being removed from synapse. It does this by blocking the reuptake pumps that are responsible for transporting dopamine back into the pre-synaptic cell. This results in a prolonged dopamine response on the post-synaptic cell and a "high." The problem is that in the long-term, your brain will sense the over-stimulation. It will respond by decreasing the number of receptors for dopamine. This causes you to feel depressed without constant use of the drug and is the basis for addiction.
Summarize the changes that occur in the brain during fetal development and early childhood. Use this to explain why it is easier for a child to learn how to speak a foreign language or how to play a musical instrument than it is for an adult.
During development (both as a fetus and in early childhood), there is a flurry of activity in the brain as neurons, somewhat randomly, make connections with one another. This peaks around the age of 2, and then the brain begins the process of pruning. Connections that are frequently used are strengthened, while those that are not used often are broken down. This process continues throughout childhood, which is why it is easier for children to learn new skills, such as speaking a foreign language or playing a musical instrument. They have more connections in their brains to accomplish a task.
Compare and contrast the following terms related to the organization of the nervous system.
A) Sensory division vs. Motor division
B) Somatic division vs. Autonomic division
C) Sympathetic division vs. Parasympathetic division
A) The sensory division brings information from sense organs to the central nervous system and the motor division takes information from the central nervous system to the muscles.
B) Both divisions are part of the motor division of the peripheral nervous system. The somatic division controls voluntary muscles (called skeletal muscles) and the autonomic division controls involuntary muscles (called smooth or cardiac muscles). The autonomic division is also further subdivided into the sympathetic and parasympathetic divisions.
C) The sympathetic division controls activities that use energy or cause action (think "superhero"). The parasympathetic division controls activities that help you gain or conserve energy (think "couch potato"). Both act on the same organs and both work together to help maintain homeostasis.
Explain how a reflex works. List several examples of reflexes.
A reflex is an involuntary response mediated by the spinal cord. Sensory information comes to the spinal cord. The signal is relayed to an interneuron, which is part of the gray matter in the spinal cord. From the interneuron, the signal is relayed to a muscle to generate a response. Thus, the information is processed without having to travel up to the brain. Five examples of reflexes are the knee-jerk, ankle-jerk, biceps-jerk, triceps-jerk, and Babinski reflex.
Identify which part of the peripheral nervous system is used for each of the following tasks. Give all levels of organization (for example, don't simply write "sympathetic division," include, "Peripheral nervous system, motor division, autonomic division, sympathetic division." Use the following terms in your answer:
Sensory division Motor division
Somatic division Autonomic division
Sympathetic division Parasympathetic division
A) Flexing your bicep
B) Feeling the fabric on a new sweater
C) Dilating your pupils
D) Increasing your heart rate
E) Digesting food (after it's swallowed)
F) Seeing a friend
G) Breathing more heavily after starting to exercise
A) motor division, somatic division
B) motor division, somatic division (to run your fingers over it) AND sensory division (to interpret the sensation)
C) motor division, autonomic division, sympathetic division
D) motor division, autonomic division, sympathetic division
E) motor division, autonomic division, parasympathetic division
F) sensory division
G) motor division, somatic division