Nervous system

Question 1

What are the two main cells in the nervous system?

Answer 1

Neurons and glia (neuroglia)

Question 2

Describe the structure of a neuron.

Answer 2

Consists of three main parts:
-Cell body (main body)
-Dendrites (branching projections that conduct impulses to cell body of neuron)
-Axon (elongated projection that conducts impulses away from cell body of neuron)

Question 3

Name the three types of neurons and their functions.

Answer 3

-Sensory (afferent) neurons - conduct impulses to the spinal cord and brain
-Motor (efferent) neurons - conduct impulses away from brain and spinal cord to muscles and glands
-Interneurons - conduct impulses from sensory neurons to motor neurons or among a network of interneurons

Question 4

What is the function of glial cells?

Answer 4

Support cells, bringing the cells of nervous tissue together structurally and functionally.

Question 5

What are the three main types, and functions of glial cells of the CNS?

Answer 5

• Astrocytes - star-shaped cells that anchor small blood vessels to neurons
  -Microglia - small cells that move in inflamed brain tissue carrying on phagocytosis
  -Oligodendrocytes - form myelin sheaths on axons in the CNS

Question 6

What is a nerve?

Answer 6

Bundle of peripheral axons

Question 7

What are the three types of nerve coverings?

Answer 7

• Endoneurium - surrounds individual fibers within a nerve
• Perineurium - surrounds a group (fascicle) of nerve fibers
• Epineurium - surrounds entire nerve

Question 8

What are tracts?

Answer 8

Bundle of central axons

Question 9

What is white matter?

Answer 9

Tissue composed primarily of myelinated axons (nerves or tracts).

Question 10

What is grey matter?

Answer 10

Tissue composed primarily of cell bodies and unmyelinated fibers.

Question 11

What is a reflex arc?

Answer 11

A neurological and sensory mechanism that controls a reflex, an immediate response to a particular stimulus. The primary components of the reflex arc are the sensory neurons (or receptors) that receive stimulation and in turn connect to other nerve cells that activate muscle cells (or effectors), which perform the reflex action.

Question 12

What is a nerve impulse?

Answer 12

A nerve impulse is a sudden reversal of the electrical charge across the membrane of a resting neuron. The reversal of charge is called an action potential. It begins when the neuron receives a chemical signal from another cell.

Question 13

Describe the mechanism of a nerve impulse.

Answer 13

1) A neuron at rest is negatively charged (or slightly positive on the outside) from a slight excess of Na+ on the outside
2) A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron
3) Inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point; this depolarization is a nerve impulse (action potential)

Question 14

What is continuous conduction?

Answer 14

The process by which an action potential moves step-by-step along an unmyelinated axon, depolarizing each successive segment of the axonal membrane.

Question 15

What is saltatory conduction?

Answer 15

In myelinated fibers, conduction can “jump” from gap to gap and this greatly speed up the rate of conduction.

Question 16

What is a synapse?

Answer 16

The place where impulses are transmitted from one neuron to another (the postsynaptic neuron).

Question 17

What are the three parts of a synapse?

Answer 17

• Synaptic knob
• Synaptic cleft
• Plasma membrane

Question 18

What is a neurotransmitter?

Answer 18

Neurotransmitters are your body’s chemical messengers. They carry messages from one nerve cell across a space to the next nerve, muscle or gland cell.

Question 19

Name some common neurotransmitters.

Answer 19

• acetylcholine (ACh)
• amines (norepinephrine, dopamine, serotonin)
• endorphins
• enkephalins
• nitric oxide (NO)

Question 20

What are the parts and functions of the brain stem?

Answer 20

• Medulla oblongata - helps control breathing, heartbeat, and blood pressure
• Pons - unconscious processes and jobs, such as your sleep-wake cycle and breathing
• Midbrain - motor control, particularly eye movements and processing of vision and hearing

Question 21

What is the function of the cerebellum?

Answer 21

Helps control muscle contractions to produce coordinated movements so that we can maintain balance, move smoothly, and sustain normal postures

Question 22

What is the function of the hypothalamus?

Answer 22

• major center for controlling the ANS; therefore helps control the functioning of most internal organs
• controls body temperature, appetite, wakefulness, and pleasure
• controls hormone secretion of the pituitary gland

Question 23

What is the function of the thalamus?

Answer 23

• relays sensory impulses to cerebral cortex sensory areas
• associates sensations with emotion
• regulates level of consciousness
• participates in motor reflexes

Question 24

What is the function of the pineal gland (pineal body)?

Answer 24

• adjusts output of “timekeeping” hormone, melatonin in response to changing levels of external light (sun and moon)

Question 25

Describe the structure of the cerebrum.

Answer 25

• largest part of the brain
• outer layer of grey matter is the cerebral cortex; made up of lobes; composed mainly of dendrites and cell bodies of neurons
• interior composed mainly of white matter (tracts - nerve fibers arranged in bundles)
• basal nuclei (islands of grey matter regulate automatic movements and posture)

Question 26

What is the function of the cerebrum?

Answer 26

Mental processes of all types, including sensations, consciousness, memory, and voluntary control of movements

Question 27

Describe the structure of the spinal cord.

Answer 27

• columns of white matter, composed of bundles of myelinated nerve fibers form the outer portion of the H-shaped core of the spinal cord; bundles of axons called tracts
• interior composed of grey matter made up mainly of neuron dendrites and cell bodies

Question 28

What is the function of the spinal cord?

Answer 28

• spinal cord tracts provide two-way conduction paths - ascending and descending
• functions as the primary center for all spinal cord reflexes; sensory tracts conduct impulses to the brain, and motor tracts conduct impulses from the brain

Question 29

What are the three layers of the cerebral and spinal meninges?

Answer 29

• dura mater - tough outer membrane
• arachnoid mater - cobweblike middle layer
• pia mater - delicate inner layer adhering to brain and spinal cord

Question 30

Where can you find CSF?

Answer 30

• central canal inside cord
• subarachnoid spaces of meninges
• ventricles in brain

Question 31

What makes up the peripheral nervous system?

Answer 31

• Cranial nerves - twelve pairs; attached to undersurface of the brain; connect brain with the neck and structures of the thorax and abdomen
• Spinal nerves - 31 pairs; contain dendrites of sensory neurons and axons of motor neurons; conduct impulses necessary for sensations and voluntary movements

Question 32

What is a dermatone?

Answer 32

Skin surface area supplied by a single cranial or spinal nerve.

Question 33

What is the function of the ANS?

Answer 33

The autonomic nervous system is a component of the peripheral nervous system that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. Helps maintain or quickly restore homeostasis.

Question 34

What is the function of the sympathetic nervous system?

Answer 34

Your sympathetic nervous system is best known for its role in responding to dangerous or stressful situations. In these situations, your sympathetic nervous system activates to speed up your heart rate, deliver more blood to areas of your body that need more oxygen or other responses to help you get out of danger.

Question 35

What is the function of the parasympathetic nervous system?

Answer 35

The parasympathetic nervous system is responsible for the body’s rest and digestion response when the body is relaxed, resting, or feeding. It basically undoes the work of sympathetic division after a stressful situation. The parasympathetic nervous system decreases respiration and heart rate and increases digestion.