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Physiology > Homeostasis/brain & Spinal Cord > Flashcards

Homeostasis/brain & Spinal Cord Flashcards

1
Q

What is homeostasis?

A

The condition of equilibrium in the body’s internal environment

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2
Q

What are the components of a feedback system?

A

Sensor ( thermo/chemoreceptors), set point (control centre eg. Brain stem), effector (response), regulated variable.

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3
Q

What is the gain of a regulated variable?

A

The precision by which a control system can prevent deviation from homeostasis
Gain = amount of correction needed / amount of abnormality after correction

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4
Q

Is a large or small gain better to maintain homeostasis ?

A

A large gain indicates that it has a more sensitive regulation that better maintains normal conditions.

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5
Q

What is a negative feedback loop?

A

Acts to reduce an effect
eg. Body temperature, when bt decreases -shivering occurs which increases heat production to return body temp towards original value.

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6
Q

What is a positive feedback loop.?

A

Acts to increase an effect
Eg. Blood clotting
Feed forward loops are physiological responses in anticipation of a change in a variable.

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7
Q

What is the difference between a reflex and local response.?

A

A reflex response requires knowledge from an integrating centre and a circuitry that connects receptor to effector.
A local response allows individual part of the body to self regulate their responses to certain conditions.

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8
Q

What’s the difference between the somatic and autonomic nervous system?

A

Autonomic - involuntary, controls smooth muscle & endocrine glands. Conducts impulses from CNS to effectors. Subdivided into para and sympathetic nervous systems.
Somatic - voluntary, conducts impulses from CNS to skeletal muscles.

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9
Q

What does the parasympathetic nervous system do?

A

Constricts pupils
Stimulates salivations digestion/bile secretion
Slows heart rate
Constricts bronchi

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10
Q

What does the sympathetic nervous system do?

A

Dilates pupils
Inhibits salivation / digestion/contractions of bladder
Increases heart rate
Dilates bronchi

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11
Q

What makes up the CNS?

A

Brain
Spinal cord
Brain stem

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12
Q

What makes up the PNS?

A

31 pairs of spinal nerves
Motor neurones
Sensory neurons
Ganglion

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13
Q

What are the 2 types of cells of the nervous system?

A
  • Neurones - nerve cells
  • glial cells - non-neuronal cells, maintain homeostasis, form myelin & support neurones.
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14
Q

How is information passed within neurones?

A

Electrically, from cell body to axon terminals via an action potential.

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15
Q

How is info passed between neurones?

A

Chemically, calcium causes neurotransmitter in synaptic vesicles to be released into the synaptic cleft, and picked up by receptors on dendrite, is above threshold, neurone Fires an action potential.

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16
Q

What are the 5 types of glial cells?

A

Schwann cells
Oligodendrocyte
Microglial cells
Ependymal cells
Astrocyte

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17
Q

What is the function of astrocyte cells?

A
  • Regulate chemicals around neurones
  • regulate blood flow around the brain
  • Nervous system repair- creating glial scars
  • maintenance of the blood-brain barrier
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18
Q

Where does oligodendrocytes form myelin sheath?

A

Axons in the CNS,
Myelin is a fatty protein rich sheath around as axons
Can myelinate up to 50 axons

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19
Q

What do Schwann cells do?

A
  • Form myelin in PNS
  • assist in regeneration & regrowth of axons
  • myelin allows axon potentials to propagate more quickly.
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20
Q

What’s the function of the microglia?

A
  • brains immune system - savage the CNS for plaque, damaged cells & infected agents
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21
Q

What are ependymal Cells?

A

Make up the ependyma membrane lining of the central canal of spinal cord. They produce cerebrospinal fluid.

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22
Q

What 3 parts make up the brainstem?

A

Medulla
Pons
Cerebellum

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23
Q

Label the basic structures of the brain

A

Spinal cord
Brainstem
Midbrain
Thalamus
Basal ganglia
Cerebral cortex

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24
Q

What does the medulla oblongata do?

A

Via chemoreceptors →
-Controls cardiac functions - heart rate & blood pressure
- respiration-breathing rate
- reflexes - vomiting, coughing

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25
Q

What does the pons do?

A

Contains nuclei that relay signals from forebrain to cerebellum - nuclei that deal with: sleep, respiration, swallowing, bladder control, hearing etc.

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26
Q

What does the cerebellum do?

A

Maintenance of balance & posture
Coordination of movements- across multiple joints
Motor learning

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27
Q

What does the midbrain do?

A
  • Tectum - controls rapid orientation of the head & neck.
    → superior colliculus - vision
    → inferior colliculus - sound
  • substantia nigra- parkinsons disease - also associated with sleep, wake cycles, alertness & temp regulation
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28
Q

What does the thalamus do?

A

Takes info from periphery to the cortex
Hypothalamus - hormones, metabolic control eg. Body temp

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29
Q

What does the basal ganglia do?

A

A series of interconnected nuclei
- movement regulation, skill learning, habit formation, selection of appropriate behaviours
( programmed movements)

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30
Q

What does the cerebral cortex do?

A

Movement
Attention
perception
Awareness
Thought
Memory
Language
Consciousness

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31
Q

What is the spinal cord?

A

First point of call for info going into & out of the CNS

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31
Q

What is the spinal cord?

A

First point of call for info going into & out of the CNS

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32
Q

In the spinal cord is gray matter on the inside or outside ?

A

Inside, white matter on outside

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33
Q

Name the layers of the spinal cord?

A

Cervical (c)
Thoracic (t)
Lumbar (L)
Sacral (s)

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34
Q

What is gray matter?

A

Neurones & other cells

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35
Q

What is white matter?

A

Fibres that carry info up & down the cord.

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36
Q

Why is there less white matter in the lower sections of the spinal cord than in the cervical?

A

Fibres join the tract above the sacral and send into up & out of the brain via the cervical, so more fibres are at the cervical top region of the spinal cord than at the sacral.

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37
Q

Where is sensory info localised in the spinal cord?

A

The dorsal horn
- info such as fine touch, proprioception, pain & temp.

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38
Q

Where are motor neurons localised in the spinal cord?

A

The ventral horn ( bottom)
- these make direct contact with the muscles (effectors), stimulation of these neurons causes movement.

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39
Q

What is somatotopy?

A

Spatial map of the body. Eg. Adjacent neurons in neural tissue respond selectively to stimuli presented to adjacent locations on the body.

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40
Q

What are the 2 major descending systems of the spinal cord?

A

Lateral & medial descending systems.

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41
Q

What tracts make up the lateral descending system of the spinal cord?

A

Corticospinal tract (goes to cortex & comes from spine)
Rubrospinal tract

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42
Q

Where are fibres of the lateral descending system of the spinal cord found & where do they connect to?

A

Fibres are in the dorsolateral ( top- outer-side) of the spinal cord.
They connect to motor neurons in the lateral part of the ventral hom - this controls lateral parts of the body eg. Legs & arms.

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43
Q

What do the corticospinal & rubrospinal tracts do?

A

Corticospinal tract strongly influences all body movement.
Rubrospinal tract can compensate almost completely for the loss descending corticospinal input.
However, the ability to use fingers individually cannot be compensated for - this is the sole province of the corticospinal system .

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44
Q

What 2 tracts make up the medial descending system of the spinal cord ?

A

Vestibulospinal & reticulospinal tracts

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45
Q

Where are fibres of the medial descending system of the spinal cord found a where do they connect?

A

Fibres are in the ventro-medial ( bottom-middle) part of the white matter.
They connect to motor neurons in the medial part of the ventral hom.

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46
Q

What do the vestibulospinal & reticulospinal tracts do?

A

Influence medial musculature, involved in the control of balance & posture - with little conscious control.
The vestibulospinal tract retains balance when the body is moved - external disturbance.
The reticulospinal tract helps us retain posture & balance during our own volitional movements - internal disturbance.

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47
Q

What are the 2 major ascending pathways of the spinal cord?

A

Medial lemniscus (dorsal column pathway)
Spinothalamic tract (lateral spinothalamic tract)

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48
Q

What does the medial lemniscus (dorsal column pathway) do?

A

Carries sensory info from the joint & skin eg. Fine touch, vibration, two-point discrimination, & proprioception

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49
Q

What does the spinothalamic tract do?

A

Conveys crude touch- a sense of being touched without knowledge of where, pain & temperature.

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50
Q

Where do the cell bodies of incoming sensory neurones lie?

A

Outside the spine in dorsal root ganglion, unlike motor neurones that have their cell bodies in the ventral horn.
Regardless of where the cell bodies are, both the sensory & motor axons run in the spinal nerves.

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51
Q

How are the 31 pairs of spinal nerves divided?

A
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccyx
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52
Q

What does position of nerves determine?

A

What part of the body each spinal nerve serves.
Because some parts of the body have more muscles & sensory receptors the size of the nerve and amount of info carried by the nerve will be different.

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53
Q

What are dermatomes ?

A

An area of skin supplied by nerves from a single spinal root.

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54
Q

What is 2-point discrimination?

A

The ability to discern that 2 nearby objects are being touched to the skin - this reflects how finely innervated an area of skin is.

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55
Q

What is a motor pool?

A

All motor neurones that innervate a single muscle.
Because there are more muscle fires than neurones, each muscle fibre is innervated by a single neurone, but a single motor neurone may innervate many fibres in the same muscle.

Muscles capable of fine movements are innovated by more neurones.

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56
Q

What is a motor unit?

A

The motor neurone & all the muscle fibres it contacts define the motor unit - they make up motor pools.
A lower motor neurone (alpha motor neurone) innervates a muscle. Each motor neurone synapses with multiple fibres within the muscle.

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57
Q

What does the dorsal horn do?

A

Contains sensory neurones, these receive sensory info & send it up to the brain.

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58
Q

What does the ventral horn do?

A

Contains motor neurones that send messages directly to the muscles

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59
Q

What do motor neurones use to signal the amount of force to be exerted by a muscle ?

A

A rate code- an increase in rate of action potentials fired by the motor neurone causes an increase in amount of force that the motor unit generates.

60
Q

What is the name given to maximal contraction of muscles?

A

Tetanic contractions - this occurs when action potentials occur in quick succession at a frequency that is so fast that the muscle cannot relax between action potentials

61
Q

What does size & recruitment principle state about force and neurones?

A

With increasing strength of input onto motor neurones, smaller motor neurones are recruited & fire action potentials before larger motor neurones are recruited.

62
Q

Describe the stretch reflex process?

A

Stretch is detected in the muscle, leading to increased activity in sensory & motor neurones that innervate the muscle, while inhibiting the motor neurons that innervate antagonists.

63
Q

What are reflexes?

A

Rapid automatic control of movement, with no voluntary control
Mainly happen in spinal cord & low in brain stem.

64
Q

What are the 2 important brainstem nuclei groups?

A

The reticular formation - a set of interconnected nuclei that are located throughout the brainstem.
The vestibular nuclei - nuclei for the vestibular system & are located in the brainstem.

65
Q

What is the vestibular system of the brainstem?

A

The sensory system that provides the sense of balance & spatial orientation for the purpose of coordinating movement with balance.
The vestibulospinal tract originates in the vestibular nuclei.
They send most of their output to the spinal cord & to the muscles that move the eyes.

66
Q

What is the reticulospinal tract?

A

The reticular formation is a set of interconnected nuclei that are located throughout brainstem. The reticulospinal tract originates in the reticular formation.
Function - maintaining tone, balance & posture
Reticulospinal - from red nucleus → spine.

67
Q

What is the superior cerebellar penduncle of the cerebellum?

A

Efferent (out) pathway of info to the cortex (through the thalamus) & to the red nucleus.

68
Q

What is the middle cerebellar peduncle?

A

Most fibres originate in the pons, input from sensory, visual, vestibular & motor systems, input is from the cortext.
- Input

69
Q

What is the inferior cerebellar penduncle?

A

Carries info to & from the spinal cord & vestibular nuclei

70
Q

What is the red nucleus?

A

A spherical collection of cell bodies in the midbrain.it receives a large input from the cerebellum & primary motor cortex.

71
Q

What are the 2 pathways in the basal ganglia?

A

Direct pathway- short loop, has an excitatory effect on context, net effect is pro- movement.
Indirect pathway- long loop, has an inhibitory effect on context, net effect is anti-movement.

72
Q

What will happen if the basal ganglia is damaged?

A

States where there’s too much or too little movement.

73
Q

What will happen is the cerebellum gets damaged?

A

States where movement can still be made, but they are uncoordinated.
Actions are hesitant & clumsy, & affects balance & gait.

74
Q

What is the cerebral hemisphere?

A

Outer surface of brain, superficially divided into several lobes which are responsible for higher reasoning.

75
Q

What is the function of the cerebellum?

A

Base of brain, important for timing, planning of movement, motor memory & posture & executing motor skills.
( co-ordinated movement).

76
Q

What is the alternative name for forebrain?

A

Prosencephalon

77
Q

What is the alternative name for mesencephalon?

A

Midbrain

78
Q

What is the alternative name for rhombencephalon?

A
  • Hindbrain
79
Q

What are the 3 ancestral regions of the vertebrate brain?

A
  • Forebrain (prosencephalon)
  • midbrain (mesencephalon)
  • hindbrain (rhombencephalon)
80
Q

By the 5th week of development what does the forebrain (prosencephalon) divide into ?

A
  • Endbrain (telencephalon)
  • interbrain (diencephalon)
81
Q

By the 5th week of development what does the hindbrain (rhombencephalon) constrict to form?

A
  • Afterbrain ( metencephalon )
  • the spinal brain ( myelencephalon)
82
Q

What makes up the telencephalon?

A

The cerebrum

83
Q

What makes up the diencephalon?

A

The thalamus, hypothalamus, & epithalamus

84
Q

What makes up the mesencephalon?

A

The midbrain (brainstem)

85
Q

What makes up the mesencephalon?

A

Pons (brainstem)
Cerebellum

86
Q

What makes up the myelencephalon?

A

Medulla oblongata (brainstem)

87
Q

What does the diencephalon do?

A
  • Receives sensory input from body & distributes to appropriate areas of the brain.
    It sits at top of brainstem & comprises the thalamus, hypothalamus, subthalamus, & epithalamus.
88
Q

Function of thalamus

A

Mediating sensation, motor activities, cortical arousal, learning & memory.
Composed of thalamic numeri that send info to & receives input from specific regions of the cortext.

89
Q

Function of the hypothalamus

A

Homeostasis - autonomic control centre, regulation of body temp, food intake, water balance, sleep-wake cycles & control of endocrine system functioning.

90
Q

Function of subthalamus

A

Subthalamic nucleus has a role in processing that occurs in the basal ganglia.- unknown

91
Q

Function of epithalamus

A

Relay station between the senses & the cerebral cortex. The pineal gland is part of the epithalamus.

92
Q

What is the midbrain?

A

Contains fibres linking the cerebral hemisphere, Cerebellum & basal ganglia.
Nuclei are involved in voluntary movement, coordination of visual & auditory reflexes, the regulation of circadian rhythms & thermoregulation.

93
Q

Are dorsal roots efferent or afferent?

A

Dorsal roots are afferent, so carry sensory info to the CNS from the PNS

94
Q

Are ventral roots efferent or afferent?

A

Ventral roots are efferent, so carry motor info from the CNS to the PNS

95
Q

What is the dorsal root ganglion ?

A

Part of the dorsal root that contains the cell bodies of the sensory nerve fibres.

96
Q

What is the spinal nerve?

A

Dorsal & ventral roots joint to from a spinal nerve, which is a mixed nerve as it carries both sensory & motor neurons.

97
Q

How many pairs of spinal nerves do humans have ?

A

31 pairs

98
Q

Where do motor neurone cell bodies reside?

A

In the spinal cord.

99
Q

What do each spinal nerve divide into ?

A

Dorsal ramus - carries motor & sensory info to & from the posterior muscles & skin
Ventral ramus- carries motor & sensory info to & from the anterior muscles & skin.

100
Q

What is a plexus ?

A

A network of intersecting afferent & efferent nerves, formed from ventral rami.
Function - to redistribute nerve fibres so that each nerve that exits the plexus will consist of fibres from a number of different spinal nerves.
4 main plexuses - cervical, brachial, lumbar & sacral.

101
Q

What is the corticospinal tract?

A

The major motor pathway which connects the upper motor neurones In the cerebral cortex to the spinal cord.
Function - to carry motor info from the 🧠 to the body for the voluntary control of the trunk & legs.
Also involved in motor swills eg. Walking. - long nerves fibres = myelinated

102
Q

What is upper motor neurone syndrome ?

A

Damage to the corticospinal tract causes dysfunction in the motor control of skeletal muscles resulting in paralysis, tenseness, spasticity, weakness, muscle twitches & spasms

103
Q

Which way do dermatomes run on the trunk?

A

Honzontally.

104
Q

Which way do dermatomes run along the arms & legs?

A

Vertically

105
Q

What is the corpus callosum ?

A

Large bundle of neuronal axons passing between the left & right hemispheres that allow communication between the two hemispheres.

106
Q

What is the cerebral cortex?

A

Composes outer layer (grey matter) of brain, involved in higher brain functioning , like reasoning, abstract thought & language.

107
Q

What does the frontal lobe do?

A

Primary motor cortex (postenior) generates nerve impulses that initiate movements. Premotor cortex (anterior) plan these movements. Prefrontal cortex ( antenor) - working memory. Broca’s area involved in speech production.

108
Q

What does the parietal lobe do?

A

Somatosensory cortex integrates sensory info (auditory, visual, somatosensory, proprioceptive info)
Primary somatosensory cortex -mapped representation of the sensory neurones corresponding to body parts. - sensory homunculus.

109
Q

What does the occipital lobe do?

A

Contains visual cortex, primary visual cortex contains a well defined map of visual info received from the outside world.

110
Q

What does the temporal lobe do?

A

Contains auditory cortex which receives & processes auditory info.
Wernicke’s area is involved in language comprehension.

111
Q

What happens in the primary motor cortex?

A

Neurones fire around 5-100 Ms before movement onset & can code for the basic parameter for movement. Eg. Force, speed.

112
Q

What happens in the pre-motor cortex?

A

Neurones code for more complex parameters of movement eg. Spatial & sensory guidance movement

113
Q

What happens in the supplementary motor cortex ?

A

Neurones code for other complex aspects of movement that are are different to those is the pre-motor cortex eg. Coordinating temporal sequences of actions.

114
Q

What happens in the primary sensory cortex ?

A

Touch-vibration, heat, pain, pressure,proprioception eg joint position sense.

115
Q

What happens in posterior parietal cortex ?

A

Integration of sensory, visual info to execute complex movement in the environment.

116
Q

What is an autocrine signal?

A

Can be signalled by the same cell

117
Q

Paracrine signal

A

Signalled by nearby cells, via cytokines.

118
Q

Signal via distant multi- cellular organisms.

A

Endocrine signalling by hormones

119
Q

What are the types of cell signals?

A

Hormones, chemical element eg. Protein, light, heat, water.

120
Q

What can signalling systems do?

A
  • warn off pathogens infections.
  • alter / regulate metabolic processes
    -Switch on or off feedback loops.
121
Q

What response does cell signalling have?

A

-Change in metabolism of cell
- change in electrical charge of csm
- change in gene expression of cell.

122
Q
  • What are Exocrine glands?
A

Secrete their products into ducts ( sweat/intestines)

123
Q

What are endocrine glands?

A

Ductless, they release hormones into the blood.

124
Q

What are hormones?

A

Chemical messengers carried by the blood to target cells.

125
Q

Why are hormones specific?

A

They only affect specific target cells, with receptors for that hormone.

126
Q

What is the function of hormones?

A
  • To regulate internal environment, metabolism & energy balance, contraction of smooth & cardiac muscle fibres, glandular secretions & some immune system activities.
  • control growth a development.
  • regulate operation of reproductive system
  • help establish circadian rhythms.
127
Q

What is the difference between the endocrine & the nervous system?

A

Endocrine- chemical messengers whereas the NS has an electrical conduit system, the endocrine system acts slow ,NS is instantaneous, endocrine system has longer lasting effects,NS is short-lived.

128
Q

What are the 3 major structural classes of hormones?

A
  • Amines eg. Thyroid Hormones, dopamine
  • peptides & proteins eg. Insulin
  • steroids eg. Cortisol, androgens (testosterone)
129
Q

Are peptide hormones soluble?

A

Yes, peptides & all catecholamine hormones are water soluble - therefore, circulate dissolved in the plasma. Some bind to plasma proteins.

130
Q

Are steroid & amine hormones soluble ?

A

No, they circulate mainly bound to plasma proteins.

131
Q

What are the major organs that remove hormones from the plasma?

A

Liver & kidneys by metabolizing or excreting them.

132
Q

What is the mechanism of hormone action?

A

Transport via blood to target tissue - receptors for hormones on or in target cells.

133
Q

Where are receptors for steroid & thyroid hormones (amine) found ?

A

Inside target cells ( lipid soluble)

134
Q

Where are receptors for peptide hormones & Catecholamine’s found?

A

On the plasma membrane

135
Q

What does the responsiveness of a target cell to a hormone depend on ?

A
  • The hormones concentration in the blood.
  • the abundance of the target cell’s hormone receptors
  • influences exerted by other hormones- 3 types of effects-
    • permissive - target cell needs two hormones
      -synergistic -2 hormones act together to have a greater effect
    • antagonistic - one hormone opposes the action of another.
136
Q

What is hormone secretion controlled by?

A
  • Plasma concentration of an ion or nutrient that the hormone regulates eg. Insulin secretion
  • neural input to the endocrine cells eg. The ANS controls hormonal secretion via the adrenal medulla & endocnne glands.
  • other hormones eg. A trophic hormone - a hormone that stimulates the secretion of another hormone eg. ( TSH)
137
Q

Motor neurons that control the upper limbs are found in which part of the spinal cord?

A

Cervical enlargement

138
Q

Which protein blocks the actin binding site during the cross-bridge cycle?

A

Tropomyosin

139
Q

The brain consumes roughly, how much of the human body’s cardiac output?

A

10 - 19%

140
Q

Which hormones are released from the anterior pituitary gland?

A

Follicle stimulating hormone
Growth hormone
Thyroid stimulating hormone
Adrenocorticotropic hormone

141
Q

What is the supplemental motor area involved in?

A

Bimanual coordination

142
Q

Which part of the feedback system receives afferent into from the regulated variable & sends a signal to the control centre?

A

Sensor

143
Q

Is skeletal muscle multinucleated & does it have a single or double neuromuscular junction per fibre?

A
  • Skeletal muscle is multinucleated & has a single neuromuscular junction per fibre.
144
Q

Can a single fibre be innovated by 2 or more motor neurons?

A

No it cannot

145
Q

Can muscles contain motor units of different sizes?

A

Yes many muscles do

146
Q

Are the biggest motor units the fastest & most fatigable?

A

Yes

147
Q

What are changes in mean arterial pressure sensed by?

A

Mechanoreceptors in the carotid sinus & aorta arch, this afferent info is processed in the medulla.

Physiology (9 decks)

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