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Fundamentals Of Physiology > Nervous System > Flashcards

Nervous System Flashcards

1
Q

What is the central nervous system (CNS)?

A

The brain and spinal column

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2
Q

What is the peripheral nervous system (PNS)?

A

Consists of nerves outside of the CNS

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3
Q

What does the CNS and PNS control?

A

The co-ordination of body systems.
In concert with the endocrine system

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4
Q

Define Neurons

A

The functional units of the nervous system.

-cannot survive long without oxygen
-they can regenerate but can’t reproduce shortly after birth.
-glial cells support neurons.

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5
Q

Define dendrites

A

-Receivers . Stimuli/impulses

-Short branching processes = increase surface area to facilitate passage of nervous impulse

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6
Q

Define cell body (soma)

A

Contains the nucleus, mitochondria (ATP), rough E.R.
Neurotransmitters

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7
Q

Define Axon

A

-conducts nerve impulses away from the cell body toward another neuron or effector cell

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8
Q

What is myelin sheath ?

A

-The cell membranes of specialised glial cells.

-insulating fatty layer that speeds transmission

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9
Q

What are Schwann cells ?

A

-cells in the PNS that form the myelin sheath around a neurons axon

-Supportive, nutritive, and service facilities for Neurons.

-Insulate nerve impulse

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10
Q

What is the gap between Schwann cells?

A

-Node of ranvier.

-works with myelin sheath to increase speed of conduction of impulses along the axon

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11
Q

What are the 3 functional types of Neurons found?

A

Sensory (afferent)

Motor (efferent)

Interneurons (between)

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12
Q

Sensory Neurons (afferent)

A

-have long dendrite and short axon and carry messages from sensory receptors to the CNS.

Somatic sensory neurones- external environment, CNS

Visceral sensory Neurons- internal environment, CNS

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13
Q

Motor Neurons (efferent)

A

-have a long axon and short dendrites.
- transmit messages from the central nervous system to the muscles (or to glands)

Somatic motor Neurons- voluntary control impulses (eg- responding to name being called)

Visceral motor Neurons- unconscious control (eg- smooth muscle/heart beating)

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14
Q

Interneurone

A

-found between sensory and motor Neurons (only in CNS)

-makes something happen (glands secrete, muscle contract).

-found in reflex arc

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15
Q

Structure of a nerve bundle

A

Nerve fibres contain many nerve axons to form bundles surrounded by connective tissue.

Each axon is surrounded by fibrous connective tissue:
-endoneurium = the connective tissue surrounding each nerve fibre.

-perineurium = binds groups of axons

-epineurium = an outer sheath which also contains blood vessels.

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16
Q

Generation of a nerve impulse
(Action potential)

A

-plasma membranes of all cells, have an unequal distribution of ions and electrical charges between the two sides of the membrane

Resting potential

17
Q

Define resting potential

A

The outside of the membrane has a positive charge, inside has a negative charge (-70mV)

18
Q

What is an action potential?

A

A temporary reversal of the electrical potential along the membrane for a few milliseconds.

Sodium gates and potassium gates open in membrane facilitate respective ions to cross.
Sodium and potassium ions reverse positions
Sodium crosses first

Nerve impulses can only go 1 way.

19
Q

Journey of action potential

A

-Begins at 1 spot on the membrane

-Spreads to adjacent areas of the membrane, propagating the message along the length of the cell membrane.

-After the passage of the action potential, there is a brief, the refractory period, during which the membrane cannot be stimulated.

-This prevents the message from being transmitted backward along the membrane.

20
Q

Steps in action potential

A
  1. At rest outside of membrane more positive inside.
  2. Na+ moves inside cell causing an action potential. Influx of positive Na+ makes inside of membrane more positive than the outside. (Depolarised).
  3. K+ions flow out of the cell, restoring the resting potential net charges. (Repolarised).
  4. Na+ions are pumped out of cell and K+ ions are pumped into cell, restoring the original distribution.
21
Q

What is a synapse?

A

the junction between a nerve cell and another nerve cell.

22
Q

What is a neuromuscular junction ?

A

Junction between nerve cell and muscle fibre.

23
Q

How does action potential pass?

A

-presynaptic neurone
To
-synaptic cleft
To
-postsynaptic neurone (muscle fibre)

Chemical messages = endocrine system.

24
Q

What are 2 possible ways action potential may occur?

A
  1. Electrical transmission = 2 cells very close together (synaptic cleft = small) - membranes may even be fused.
    Action potential passes directly causing depolarisation in the connected neurone.
  2. Chemical transmission = at presynaptic side of cleft, releases a neurotransmitter which diffuse across the gap causing a depolarisation of the postsynaptic neurone.
    =most common method in mammalian nervous systems.
25
Q

Where are neurotransmitters stored?

A

In small synaptic vesicles clustered at the tip of the axon.

(E.g- acetycholine, adrenalin, noradrenaline)

Action potential causes some vesicles to discharge contents.

26
Q

Neurotransmitters are either:

A
  1. Destroyed by specific enzymes in the synaptic cleft, released by postsynaptic neurone
  2. Diffuse out of the cleft
  3. Are reabsorbed by the cell.

The time for neurotransmitter action is between 0.5 and 1 millisecond.

27
Q

Autonomic nervous system (ANS)

A

-contols the body’s internal environment in a coordinated manner.

Helps control:
-heart rate
-blood pressure
-digestion
-respiration
-blood pH
-other bodily functions

Controls are done automatically, below the conscious level
In the ANS there are 2 nerves between CNS and organ

Facilities 2 diversions of control:
Sympathetic and parasympathetic

28
Q

Sympathetic = ‘’fight or flight’’ branch of ANS

A

Emergency situations, where the body needs a sudden burst of energy, are handled by the sympathetic system.

Can live without as only needed in life or death situations.

29
Q

What does the sympathetic system increase?

A

-cardiac output
-pulmonary ventilation
-routes blood to muscles
-raises blood glucose
-slows digestion
-kidney filtration

30
Q

Parasympathetic = ‘’rest and digest’’ =. Branch of the ANS

A

Normal maintenance of body acquiring building blocks and energy from food and getting rid of the wastes.

Does not ‘’go off’’ together; activities initiated when appropriate

Vagus nerve is the main parasympathetic nerve.

31
Q

What has central control of the ANS

A

The hypothalamus

32
Q

What is the role of the hypothalamus ?

A

Involved in the coordination of the ANS response

33
Q

What are the 2 types of reflex arc?

A

-monosynaptic
-polysynaptic

A nervous response without conscious thought

Fundamentals Of Physiology (20 decks)

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