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Nervous System. Flashcards

1
Q

What are neurons?

A

The basic structural and functional units of the whole nervous system

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2
Q

What are two classifications of neurons

A

Functional and structural

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3
Q

Nerve

A

A bundle of nerve fibres held together by connective tissue

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4
Q

Neuron structure consists of?

A

Cell body,dendrites and the axon

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5
Q

What is the Cell body and its function

A

contains the nucleus
- responsible for controlling the functioning of the cell
- around nucleus, is cytoplasm containing organelles

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6
Q

Dendrites and its function

A
  • short extensions of the cyotplasm of the cell body
  • carry messages, nerve impulses into the cell body
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7
Q

Axon and its function

A
  • sinle long extension of the cytoplasm
  • caries nerve impulses away from cell body
  • length varies
  • at its end, it divides into small branches
  • each branch terminates at the axon terminal
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8
Q

Axon terminal

A

forms synapse with next neuron

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9
Q

Nerve fibres

A
  • any long extension of a nerve cell, usual refers to axon
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10
Q

What is a Myelin sheath?

A
  • a layer of fatty material that covers the axon
  • nerve fibres that have a myelin sheath is called myelinated fibres
  • those that don’t = unmyelinated
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11
Q

Myelin sheath formation

A
  • outside brain and spinal cord, it is formed by special cells called Schwan cells, which wrap around axon
  • outermost coil of the schwan cell forms a neurilemma around myelin sheath
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12
Q

Neurilemma?

A

helps in the repair of injured fibres

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13
Q

Myelin three important functions?

A
  • it acts as an insulator
  • protects axon from damage
  • speeds up movement of nerve impulses along the axon
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14
Q

Nodes of Raniver

A

a gap in the myelin sheath of a nerve fibre

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15
Q

3 types of functional neurons

A

Sensory neurons (or afferent/receptor neuron)
- Carry messages from receptors in the sense organs, or skin, to the CNS (brain and spinal cord)

Motor neurons (or efferent/effector neuron)
- Carry messages from the CNS to the muscles and glands, the effectors.

Interneurons neurons (or relay/association/connector)
- Link between sensory and motor neurons.

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16
Q

3 types of structural neurons

A

Multipolar neurons
- One axon and multiple dendrites extending from cell body
- Most common.
- Includes motor neurons and most interneurons in CNS

Bipolar neurons
- One axon and one dendrite
- both have many branches from the end
- Occur in eye, ear + nose where they take impulses from receptors to other neurons.

Unipolar/Pseudounipolar neurons
- One extension only
– an axon, with a cell body to the side of the axon.
- Most sensory neurons.

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17
Q

speed of nerve impulses in fibres can be varied by?

A
  • Impulses in unmyelinated fibres travel at maximum speed of 7km/h compared with up to 500km/h in myelinated fibre.
  • Due to “jumping conduction” between noes of Ranvier.
  • Diameter of fibre
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18
Q

Two types of electrical charge

A
  • positive and negative
  • Like charges repel each other and unlike charges attract each other.
  • When unlike forces are separated, an electrical forces tends to pull them together.
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19
Q

What is the membrane potential?

A

The difference in concentration of ions inside the cell and outside the cell

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20
Q

Membrane potential is maintained due to

A

ions dissolved in extracellular and intracellular fluid:
- extracellular fluid: High concentration of sodium chloride forming Na+ and Cl- ions
- intracellular fluid: High concentration of K+
- Variety of organic substances form negative ions
- mainly due to the difference in the distribution of potassium and sodium ion on either side of cell membrane
- inside is negative relative to outside

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21
Q

Resting membrane potential

A
  • -70 mV
  • due to difference in distribution of ions in/out of cell.
  • Tendency for K+ ions to diffuse out creates negative charge inside cell
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22
Q

Potential difference is maintained by?

A
  • Sodium-potassium pump: Actively moves 3 Na+ out of the cell and 2 K+ into the cell.
  • Difference in permeability(ability of ions to cross membrane) of ions: K+ is highly permeable, Na+ is slightly permeable and large -ve ions inside are impermeable
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23
Q

List and describe 4 types of ions channels

A

1) Leakage channels: Open all the time
2) Ligand-gated channels:
- Open in response to a stimulus (“ligand”)
- Often a chemical messenger such as neurotransmitter
3) Voltage-gates channels:
- Open in response to change in membrane potential.
- Time-dependent – open after a delay
4) Ion pumps: Carriers (not channels) that carry out active transport to “pump” ions against their concentration gradient

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24
Q

4 steps of a sodium-potassium pump

A

1) pump binds three sodium ions and a molecule of ATP
2) splitting of atp provides energy to change the shape of the channel, sodium ions are driven through
3) sodium are realsed to the outside of membrane, new shape of the channel allows two potassium ions to bind(from outside of membrane)
4) release of phosphate (Atp molecule) allows channel to revert to OG form, releasing potassium ions inside of membrane

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25
Q

How membrane is polarised

A
  • INSIDE OF CELL MORE NEGATIVE THAN OUTSIDE
  • Due to higher permeability of K+ and the sodium-potassium pump, there is a net flow of positive charge out of the cell.
  • Negative organic ions inside the cell
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26
Q

Action potentials?

A

rapid depolarisation and repolarisation of the membrane.

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27
Q

Steps of action potential

A

1) Depolorisation 1
2) Depolarisation 2
3) Repolarisation
4) Hyperpolarisation

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28
Q

Depolarisation 1

A

(to Threshold)
- -70mV
-Stimulus (neurotransmitter or sensory receptor) opens ligand-gated sodium ion channels
- more sodium ions begins to flows into the cell, making intracellular fluid less negative.
- Membrane begins to become depolarised (inside of cell becomes less negative)

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29
Q

Delopolarisation 2

A

(Rising phase of action potential)
- If depolarisation reaches threshold of -55mV, voltage-gated sodium ion channels open
- sodium ion influx continues independent of the stimulus – size of the response not dependent on the size of the stimulus (all-or-none response).
- Inward movement of sodium ions results in inside of membrane becoming more positive than the outside.
- Membrane potential reaches ~ +40mV.
- Membrane said to be depolarised.

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30
Q

Repolarisation

A

(Falling phase of action potential)
- Sodium channels close stopping the influx of sodium ions
- Voltage-gated potassium channels (slower to respond than voltage-gated sodium ion channels) open.
- Flow of potassium out of the cell returns the membrane potential to negative (repolarisation)

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31
Q

Hyperpolarisation

A

(and return to resting state)
- Potassium channels open longer than needed resulting in membrane potential dropping below resting membrane potential (hyperpolarisation/undershoot).
- Extended opening of potassium channels and sodium/potassium pump action result in undershoot (hyperpolarisation).
- potassium channels close (Na+/K+ pump continues) and resting membrane potential restored.

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32
Q

What is a Refractory period

A
  • a short period following a stimulus during which a nerve cell or muscle fibre cannot be stimulated again
  • Membrane cannot undergo another action potential from time threshold is reached until resting membrane potential restored – refractory period.
  • Prevents the nerve impulse going backwards along the nerve fibre
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33
Q

How will a strong impulse affect action potential

A
  • cause more nerve fibres to depolarise
  • Produce more nerve impulses in given time.
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34
Q

What is a nerve impulse?

A

an electrochemical change that travels along the membrane of a nerve cell

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35
Q

4 steps of Transmission of nerve impulse?

A
  • A single action potential occurs in one section of a membrane.
  • it triggers an action potential in the adjacent section of the membrane
  • an action potential does not travel along the nerve fibre – the message/nerve impulse does.
  • The process is likened to a line of dominoes
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36
Q

4 steps of TRANSMISSION ALONG UNMYELINATED FIBRES

A
  • Depolarisation of one area of the membrane, causes movement of sodium ions into next section.
  • Results in opening of voltage-gated sodium channels
  • Initiates action potential
  • Process repeats along whole length of the membrane.
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37
Q

What is a synapse?

A

is the very small gap between one neuron and the next.
- Due to gap, action potentials/nerve impulses cannot continue to next neuron.

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38
Q

5 steps of TRANSMISSION ACROSS A SYNAPSE

A
  • Nerve impulse reaches axon terminal activating voltage-gated calcium ion channels.
  • calcium ions flow into cell at presynaptic axon terminal.
  • Causes synaptic vesicles to fuse with membrane, releasing neurotransmitters into the gap
  • Neurotransmitters diffuse across the gap and attach to receptors on the next neuron.
  • Stimulates ligand-gated protein channels to open, allowing influx of sodium ions and initiating an action potential.
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39
Q

Two main parts of the nervous system are?

A

central nervous system and the peripheral nervous system

40
Q

The peripheral nervous system is divided into

A
  • The afferent (sensory) division – carries impulses into the CNS.
  • The efferent (motor) division – carries impulses away from the CNS.
41
Q

What neurons make up afferent division?

A

Somatic sensory neurons – from skin + muscle.
Visceral sensory neurons – from internal organs

42
Q

What divisions make up efferent division?

A

Somatic division – takes impulses to the skeletal muscles
Autonomic division – takes impulses from CNS to heart, involuntary muscles and glands.

43
Q

6 functions/charateristics of autonomic divisions

A
  • control of the body’s internal environment - involved in many mechanisms that keep it constant.
  • E.g. heart rate, blood pressure, body temperature
  • Operates without conscious control – regulated by medulla, hypothalamus and cerebral cortex.
  • ANS nerve fibres are in both cranial and spinal nerves and carry impulses to heart muscles and muscle of other important organs/glands EFFECTOR
  • Pathway consists of two neurons – one with cell body in CNS(myelinated), the other in a ganglion.(unmyelinated)
  • effect: excitation or inhibition
44
Q

What divisions make up autonomic division? and functions and releases

A

Sympathetic division – active during stress/ ‘fight-or-flight’
- produces responses that prepare body for strenuous physical activity (fight-or-flight)
- never-ending release noradrenaline, carries impulse to effector
Parasympathetic division – active during normal function
- controls responses that maintain body in quiet conditions
- nerve endings release acetylcholine

45
Q

7 functions/characterisitc of somatic divison

A

-SNS nerve fibres are carried to skeletal muscle(EFFECTOR)
- Response to external environment
- pathway consists of one neuron: carries impulse from the CNS to the effector; no synapse and no ganglion
- operate with conscious control (voluntary)
- (neurotransmitter) acetylcholine carries impulse to effector
- receives one set of nerve fibres
- effect on target organ: excitement

46
Q

What are fight or flight responses?

A
  • At rest, sympathetic and parasympathetic systems are balanced (ANS is not inactive under normal circumstances).
  • In threatening situations the balance is upset and sympathetic becomes dominant.
  • fight-or-flight or alarm reaction become activated – prepares body for increased activity.
47
Q

6 examples of fight or flight responses?

A
  • ↑ rate + force of heart contractions and subsequent ↑ blood pressure
  • Blood vessels involved in strenuous activity dilate (E.g. in skeletal muscles).
  • Those not involved constrict.
  • ↑ breathing rate + depth, airways in lungs dilate.
  • ↑ blood glucose level (liver converts glycogen)
  • ↑ secretion from sweat glands
  • Adrenal medulla releases hormones adrenaline and noradrenaline to prolong/intensify response.
48
Q

What are the Effects of sympathetic stimulation on heart, lungs, stomach,intestine

A

Heart: Increases rate and strength of contraction, which increase blood pressure to increase o2 and blood
Lungs: Dilates bronchioles, rate/depth of breathing increase allowing more o2 for respiration
Stomach, intestines: Decreases movement

49
Q

What are the Effects of sympathetic stimulation on liver, iris of eye, sweat and salivary glands?

A

Liver: Increases breakdown of glycogen and release of glucose, more glucose for respiration
Iris of the eye: Dilates pupil, allow more light in, sharper vision
Sweat glands:Increases sweat secretion, to lose more added heat from respiration
Salivary glands: Decreases secretion of saliva

50
Q

What are the Effects of sympathetic stimulation on blood vessels of skin, skeletal muscle and internal organs?

A

Blood vessels of:
- Skin: Constricts vessels
- Skeletal muscle : Dilates vessels
- Internal organs: Constricts vessels (except heart + lungs)

51
Q

What are the Effects of sympathetic stimulation on urinary bladder and adrenal medulla

A

Urinary bladder: Relaxes muscles of wall
Adrenal medulla: Stimulates hormone secretion(noradrenaline and adrenaline) which intensify and prolong the response to speed up processes.

52
Q

What are the effect of parasympathetic stimulation on heart, lungs, stomach/intenstines?

A

Heart: Decreases rate and strength of contraction
Lungs: Constricts bronchioles
Stomach/instesntines: Increases movement

53
Q

Effect of parasympathetic stimulation on liver, iris of eye and sweat and salivary glands?

A

Liver: Increases uptake of glucose and synthesis of glycogen
iris of eye: Constricts pupil
Sweat glands: No effect
Salivary glands: Increases secretion of saliva

54
Q

Effect of parasympathetic stimulation on blood vessels of skin, skeletal muscle and internal organs

A

Blood vessels of:
- skin:Little effect
- skeletal muscle: No effect
- internal organs: Little effect

55
Q

Effect of parasympathetic stimulation on urinary bladder and adrenal medulla

A

urinary bladder: Constricts muscles of wall
adrenal medulla: No effect

56
Q

What is the PERIPHERAL NERVOUS SYSTEM?

A

Consists of nerve fibres which carry information to and from the CNS and groups of nerve cell bodies (ganglia) which lie outside the brain and spinal cord.

57
Q

PNS includes…?

A
  • 12 pairs of cranial nerves – arise from brain.
  • E.g. optic nerve, auditory nerve.
  • 31 pairs of spinal nerves – arise from spine and joined to spinal cord by two roots:
    ->Ventral root – contains only axons of motor neurons (cell bodies in grey matter)
    ->Dorsal root – contains axons of sensory neurons (cell bodies in dorsal root ganglion).
58
Q

Similarities of endocrine and nervous system

A
  • Some substances (E.g. noradrenaline, ADH + dopamine) are both hormones and neurotransmitters
  • Some hormones (E.g. oxytocin, adrenaline) are secreted into extracellular fluid
  • Some hormones + neurotransmitters have same effect on target cells (E.g. noradrenaline + glucagon both cause glycogen breakdown by liver)
59
Q

COMPARISON OF HORMONAL aka endocrine(H) + NERVOUS CONTROL aka nervous(N)

A

nature of message: Hormones (H) + electrical impulses and neurotransmitters (N)

transport of message: by the bloodstream(H) + along the membrane of neurons(N)

cells affected: all body cells (H) + muscle and gland cells (N)

type of response: may be very general and widespread(H) + usually local and specific (N)

time taken to response: slower (H) + rapid (N)

duration of response: longer lasting (H) + brief (N)

60
Q

What are receptors?

A
  • Structure that is able to detect a change in the body’s internal or external environment.
  • Can be grouped together in a sense organ (E.g. eye or ear) or a specialised nerve endings in parts of the body (E.g. skin).
61
Q

What are 6 types of receptors?

A

Thermoreceptor
osmoreceptors
Chemoreceptor
Mechanoreceptors
Nociceptors
Photoreceptors

62
Q

thermoreceptors, what do they detect and where are they found

A
  • Able to respond to heat and cold.
    DETECT:
    External temperature:
  • Detected by thermoreceptors in SKIN
  • Send information to HYPOTHALAMUS

Internal temperature:
- Monitored by thermoreceptors in the hypothalamus
- detect the temperature of the blood flowing through the brain.

63
Q

osmoreceptors, what do they detect and where are they found

A
  • Located in HYPOTHALAMUS
  • Sensitive to osmotic pressure and respond to very small changes
  • Osmotic pressure is determined by concentration of substances dissolved in blood plasma.
  • Stimulate hypothalamus so the body’s water content is maintained within very narrow limits.
64
Q

chemoreceptors, what do they detect and where are they found

A
  • Stimulated by particular chemicals
  • Found in the MOUTH AND NOSE
  • give sensitivity to taste and smell.
  • Some internal chemoreceptors are sensitive to composition of body fluids.
  • E.g. In BLOOD VESSELS – sensitive to pH and CO2/O2 concentrations, involved in regulation of the heartbeat and breathing.
65
Q

MECHANORECEPTORS, what do they detect and where are they found

A
  • Found mainly in the SKIN
  • detect touch
    Different types:
    1) Close to surface - sensitive to light touch.
  • More numerous in sensitive areas (E.g. lips, fingertips)
    2) Deeper in the skin - sensitive to pressure and vibrations.
  • The ear contains specialized mechanoreceptors which detect vibrations caused by sound.
66
Q

NOCICEPTORS, what do they detect and where are they found

A

aka pain receptors
- Stimulated by damage to tissues such as :
- a cut/heavy bump
- poor blood flow to a tissue
- excessive stimulation from stimuli such as heat or chemicals

  • Concentrated in SKIN and mucous membranes (lining of internal structures).
  • Not present in the brain.
  • Don’t adapt quickly.
  • Therefore pain continues, or worsens, while the stimulus is present – protective function.
67
Q

PHOTORECEPTORS, what do they detect and where are they found

A
  • Respond to light
  • Two types in the eye – rods and cones
  • Large amounts and tightly packed in the RETINA
  • Responsible for converting light into signals that are sent to the brain
68
Q

What is a reflex

A

a rapid, automatic response to a change In the external or internal environment; tries to restore homeostasis

69
Q

What are the 4 properties of a reflex

A
  • Stimulus: requires a trigger
  • involuntary: without conscious thought
  • rapid: small numbers of neurons involved
  • stereotyped: occurs same way each time
70
Q

Reflex arc

A
  • Pathway nerve impulse follows
    1) Receptor (either ending of sensory neuron or associate specialised cell)
    – reacts to change in internal or external environment by initiating nerve impulse in sensory neuron.
    2) Sensory neuron – carries impulse from receptor to CNS.
    3) Synapse – at least one.
  • Usually one or more interneuron but may be passed directly to motor neuron.
    4) Motor neuron – carries impulse to effector
    5) Effector – receives nerve impulse and carries out response.
71
Q

Why does awareness occur after the response has been initiated in the reflect arc

A
  • impulse sent to effector first and then the brain
  • ensures response is as fast as possible to minimise danger
72
Q

The CNS is made up of… and function

A
  • Brain and spinal cord
  • Incoming messages are processed, and outgoing messages initiated.
  • Nerves carrying these messages in/out of CNS make up the PNS.
73
Q

What is the cerebrum and function

A
  • Biggest part of brain
  • Highly convoluted (folded) surface (cerebral cortex) increases surface area.
  • Involved in:
    -> Mental functions - Thinking, reasoning, learning, intelligence, memory, sense of responsibility
    -> Perception of senses
    ->Control of voluntary muscle contractions.
74
Q

The 5 lobes of the cerebrum?

A
  • Convolutions divide each hemisphere into four lobes
    Frontal lobe
    Parietal lobe
    occipital lobe
    temporal lobe
    Insula
75
Q

Function of frontal lobe?

A

Thinking, problem solving, emotions, personality, language and control of movement

76
Q

Function of parietal lobe?

A

Processes information about temperature, taste, touch and movement

77
Q

Function of Occipital lobe?

A

Vision

78
Q

Function of temporal lobe

A

Processing memories and linking with senses; receives auditory information

79
Q

Function of insula

A

Recognition of different senses and emotions, addiction and psychiatric disorders

80
Q

Tracts? and function

A
  • Bundles of myelinated nerve fibres within white matter of brain.
  • Three types of tracts occur in the white matter:
    ->Tracts connecting areas of cortex within same hemisphere
    ->Tracts carrying impulses between left + right hemisphere
    ->Tracts connecting to other parts of brain or spinal cord.
81
Q

Corpus callosum? and function

A
  • Wide band of nerves lying underneath cerebrum at the base of the longitudinal fissure.
  • Nerve fibres cross from one hemisphere to another
  • Allows communication between two sides of cerebrum.
82
Q

Cerebellum and function?

A
  • Lies under rear part of cerebrum.
  • Outer layer of grey matter, inner layer of white matter.
  • Controls posture, balance and fine coordination of voluntary muscle.
  • Receives sensory information from inner ear (posture + balance) and stretch receptors in skeletal muscles.
  • Don’t have conscious control over
  • Without the cerebellum, movements would be jerky and uncontrolled (not smooth).
83
Q

HYPOTHALAMUS and function

A
  • Lies in the middle of the brain and is above the pituitary gland.
  • Mostly concerned with homeostasis – maintaining constant environment for cells.
84
Q

MEDULLA OBLONGATA and function?

A
  • Continuation of the spinal cord – lower medulla becomes spinal cord
  • Contains vital control centres:
    ->Cardiac Centre – regulates heart beat
    ->Respiratory Centre – controls rate + depth of breathing
    ->Vasomotor Centre – regulates blood vessel diameter
  • Also regulates reflexes of swallowing, coughing, sneezing + vomiting.
  • Regulated by hypothalamus.
85
Q

Spinal cord? and function

A
  • Enclosed in vertebral canal + extends from base of the skull to second lumbar vertebra (waist level)
  • Consist of white + grey matter.
    ->White matter arranged in ascending tracts (sensory axons carrying messages TO brain) and descending tracts (motor axons carrying messages AWAY from brain)
    Functions:
  • Carry sensory impulses to the brain + motor impulses away from the brain
    E- nable reflex actions
86
Q

Cerebral cortex

A
  • outer surface of grey matter
  • Divided into 3 functional areas:
  • Sensory areas – interpret impulses from receptors
  • Motor areas – control muscular movement
  • Association areas – intellectual and emotional processes
87
Q

White matter?

A
  • below cortex
  • consists of bundles of myelinated fibres
88
Q

Basal ganglia?

A
  • Additional grey matter deep inside cerebrum
  • Groups of nerve cell bodies associated with skeletal muscle control
  • initiate desired movements and inhibit unwanted movement
89
Q

A longitudinal fissure?

A
  • a deep cleft that almost separates the cerebrum into two halves, the cerebral hemispheres
90
Q

Convulsions?

A

folds of the surface of cerebrum

91
Q

Sulci?

A

shallow downfolds of the surface of cerebrum

92
Q

What 3 structures protect the CNS?

A

1) Bone
2) Membranes – called meninges
3) Fluid – called cerebrospinal fluid

93
Q

Bone and function

A
  • Outermost protective layer.
  • Cranium (part of skull) protects brain
  • Spinal cord runs through an opening in vertebrae called the vertebral canal.
94
Q

Meninges, layers and functions

A

Covering entire CNS (inside bones) are three layers of connective tissue forming membranes(meninges)
- Outer layer (dura mater):
->Tough + fibrous – similar texture to dishwashing gloves
->Sticks closely to bone of skull, not as close in vertebral column.

-Middle layer (arachnoid):
->Loose mesh of fibres

-Inner layer (pia mater):
->Very delicate
->Contains many blood vessels
->Sticks close to surface of brain +
spinal cord

95
Q

What is cerebrospinal fluid?

A
  • Clear, watery fluid containing a few cells and some glucose, protein, urea + salts.
  • Occupies space between middle and inner layer of meninges.
  • Also circulates through cavities in the brain and through canal in centre of spinal cord.
96
Q

Three functions of cerebrospinal fluid?

A

Protection: Acts as shock absorber – cushions blows/shocks CNS sustains.

Support: Supports the brain as it is suspended in the fluid

Transport: Formed from blood + circulates through CNS before returning to capillaries.
- Circulation allows delivery of nutrients/removal of wastes from CNS

sturdy (6 decks)

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