Chapter 11.1 Thestructures and process of he nervous system

Question 1

Homeostasis

Answer 1

The state of relative stability within the body

- critical for survival because the body can only survive within a narrow range of conditions

Question 2

The _____ system regulates body structures and processes to maintain ______ despite fluctuations in the _______ and ____ environment.

Answer 2

• nervous
• homeostasis
• internal
• external

Question 3

The nervous system consist of

Answer 3

brain
spinal cord
nerves that emerge

Question 4

The nervous system has 2 major divisions

Answer 4

• The CNS

- The PNS

Question 5

Together the CNS and PNS

Answer 5

control sensory input, integration and motor output

Question 6

Somatic system

Answer 6

• part of PNS
• associated with the voluntary control of body movements through the skeletal muscles and mediation of involuntary reflex arcs.
• Consist of sensory receptors in the head and extremities, nerves that carry instructions from the CNS to the skeletal muscles
• it is involved in the relay of sensory and motor information to and from the CNS; therefore, it consists of motor neurons and sensory neurons.

Question 7

What does the CNS consist and what does it do?

Answer 7

• brain and spinal cord

- Integrates and processes information sent by nerves

Question 8

what does the PNS contain

and what does it do?

Answer 8

• includes nerves that carry sensory messages to the CNS and nerves that send info from the CNS to the muscles and glands
• Includes somatic and autonomic

Question 9

Autonomic

Answer 9

Control glandular secretions and the functioning of smooth and cardiac muscles

• not voluntary
• contains sympathetic and parasympathetic

Question 10

Sympathetic nervous system with ex:

Answer 10

prepares body for stress related activities

• dilates pupil
• increase heart rate
• inhibits digestion
• dilates bronchi

Question 11

Parasympathetic nervous system with ex:

Answer 11

• returns body to routine, day to day operations
• contricts pupil
• slower heart rate
• stimulates digestion
• constricts bronchi

Question 12

The nervous system is composed of 2 main types of cells:

Answer 12

Neurons and glial cells (cells that support the neurons)

Question 13

Neurons and the three things they do:

Answer 13

• the basic structural and functional units of the nervous system

1. respond to physical and chemical stimuli
2. conduct electrochemical signals
3. release chemicals that regulate various body processes

Question 14

Glial cells

Answer 14

• outnumber neurons by about 10-1
• They account for about half of the volume of the nervous system
• nourish neurons, remous their wastes and defend against infection
• provides a supporting framework for al the nervous-system tissue

Question 15

nerves

Answer 15

Individual neurons organized into tissues

• made up of nerve bundle(s) surrounded by protective connective tissue
• extend neurones throughout the PNS

Question 16

Sensory input

Answer 16

Sensory neurons gather info from the sensory receptors (senses) and transmit these impulses to the CNS

Question 17

Integration

Answer 17

Interneurons are found entirely within the CNS. They act as a Link between the sensory and motor neurons. They process and integrate incoming sensory info and relay outgoing motor info.

Question 18

Motor output

Answer 18

Motor neurons transmit information from the CNS to the muscles, glands and other organs

Question 19

Reflexes with ex:

Answer 19

Sudden unlearned, involuntary responses to certain stimuli

• Jerking your hand away from a hot object
• Blinking from a sudden object
• Vomiting from irritable food

Question 20

Reflex arcs (2)

Answer 20

Simple connections of neurons that explain reflexive behaviours
- use very few neurons to transmit messages (very rapid)

Question 21

Why do you feel pain after you have done a withdrawal action?

Answer 21

A reflex arc moves directly to and from the brain or spinal cord, before the brain centres involved with voluntary control have time to process the sensory information.

Question 22

Neurons may have different types and shapes but generally, they share four common features:

Answer 22

1. Dendrites
2. Cell body
3. An axon
4. Branching ends

Question 23

Dendrites (2)

Answer 23

• Short branching terminals that receive nerve impulses from other neurons or sensory receptors and relay the impulse to the cell body.
• numerous and highly branched which increases the surface area available to receive information

Question 24

Cell body (3)

Answer 24

• Contains the nucleus
• the site of the cell’s metabolic reactions
• process input from the dendrites, if the input is large enough, the cell body relays it to the axon, where an impulse is initiated

Question 25

Axon

Answer 25

• conducts impulses away from the cell body

Question 26

Axon terminal

Answer 26

• releases chemical signals into the space between it and the receptors or dendrites of neighbouring cells to communicate with adjacent neurons, glands or muscles.

Question 27

myelin sheath (3)

Answer 27

• Fatty insulating layers
• protects myelinated neurons
• speeds the rate of nerve impulse transmission

Question 28

Schwann cells (5)

• grey/white
• pns

Answer 28

• type of glial cell
• form myelin by wrapping themselves around the axon
• myelinated= white matter
• unmyelinated= grey matter
• most neurons in PNS are myelinated

Question 29

How is nerve conduction different from electrical

Answer 29

• more complex and slower
• Nerve conduction depends on the movement of ions across the cell membrane of the axon, not the movement of electrons along an electrical wire

Question 30

In a resting neuron, the cytoplasmic side of the membrane is:

Answer 30

negative relative to the extracellular side

Question 31

resting membrane potential

Answer 31

the potential difference across the membrane in a resting neuron is a form of potential energy

• 70mv
• negative on the inside relative to the outside
• provides energy for the generation of a nerve impulse in response to an appropriate stimulus

Question 32

Polarization and how do neurons become polarized?

Answer 32

The process of generating a resting potential of -70mv

• large protein molecules that are negatively charged present in the intracellular fluid but not the outside of the cell do not pass out of the cell as they are too big
• membrane is impermeable to smaller negatively charged ions such as CL
• Sodium potassium pump

Question 33

Sodium potassium exchange pump

Answer 33

• uses ATP to transport sodium ions out of the cell and potassium ions into the cell
• three sodium for two potassium
• excess passive accumulates outside of the cell
• Na and K+ still diffuses across the cell following concentration gradient but potassium ions are able to diffuse out of the cell more easily then sodium can move in so positive outside

Question 34

a nerve impulse consists of a series of

Answer 34

action potentials

Question 35

In myelinated neurons, action potential occur only at:

Answer 35

Nodes of ranvier because the myelin sheath insulates the axonal membrane that it encircles

Question 36

depolarized

Answer 36

A neuronal membrane is said to be depolarized if the transmembrane potential is reduced to less than the resting potential of -70mv.

Depolarization is caused when positively charged sodium ions rush into a neuron with the opening of voltage-gated sodium channels.

Question 37

action potential

Answer 37

if the membrane at the node of ranvier becomes depolarized to -55mv, a dramatic change occurs in the membrane. This is action potential

• all or none event. any depolarization to -55mv to any other amount up to 0 will produce identical action potentials
• brief reversal of electric polarity

Question 38

Threshold potential

Answer 38

-55mv

Question 39

repolarized

Answer 39

returned to its previous polarization

Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels. Carry positive charge out of the neuron.

Question 40

refractory period

Answer 40

the brief time where the membrane cannot be stimulated to undergo another action potential

Question 41

Saltatory conduction

Answer 41

describes the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal in comparison with the slower continuous progression of depolarization spreading down an unmyelinated axon.

• the conduction of an impulse along a myelinated neuron

Question 42

multiple sclerosis

Answer 42

The breakdown of the myelin sheath surrounding the axons in the CNS

Question 43

Synapse

Answer 43

The connection between two neurons or a neuron and an effector

Question 44

Neuromuscular junction

Answer 44

synapse between a motor neuron and a muscle cell

Question 45

Synpatic cleft

Answer 45

most neurons are not directly connected but have a gap between them
Neurons are not close enough for the impulse to jump from one to the other.

Question 46

Neurotransmitter

Answer 46

chemical messengers
carry the neural signal from one neuron to another.
can also carry neural signal from a neuron to an effector such as a gland or muscle fibre

Question 47

Explain how signal transmit across a synapse

Answer 47

When action potential arrives at the end of the neuron, the impulse causes sacs that contain neurotransmitters to fuse with the membrane of the axon.

These sacs called synaptic vesicles release their contents into the synaptic cleft by exocytosis.

The neurotransmitter diffuse across the synapse to reach the dendrites of the postsynaptic neuron or cell membrane of an effector.

neurotransmitter bind to specific receptor proteins in the membrane and trigger ion specific channels to open.

Question 48

if neurotransmitter is excitatory:

Answer 48

receptor proteins will trigger ion channels that open to allow positive ions such as sodium to flow into the postsynaptic Neuton. As a result, the membrane becomes depolarized.

the membrane of the neuron cannot experience an action potential but it lowers threshold level. The combined effect of all the stimuli spreads across the cell body. if the excitatory stimuli is strong enough, the depolarization will reach the point at which the axon is connected to the cell body and impulse will be generated

Question 49

If the neurotransmitter is inhibitory:

Answer 49

The receptor will trigger potassium ions to flow out resulting in more negative transmembrane potential and hyper polarization.

Question 50

After the neurotransmitter has had its effect:

Answer 50

Enzymes break it down and inactivate it so that its components can be reabsorbed by the presynaptic cell

Question 51

Acetylcholine

Answer 51

A neurotransmitter that crosses a neuromuscular junction.

Excites the muscle cell membrane, causing depolarization and contraction of the muscle fibre

Question 52

cholinesterase

Answer 52

an enzyme that breaks down acetylcholine so it can be removed from the protein receptors allowing the ion channels to close and membrane to repolarize.