Homeostasis/brain & Spinal Cord Flashcards
1
Q
What is homeostasis?
A
The condition of equilibrium in the body’s internal environment
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.
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
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.
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.
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.
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.
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.
9
Q
What does the parasympathetic nervous system do?
A
Constricts pupils
Stimulates salivations digestion/bile secretion
Slows heart rate
Constricts bronchi
10
Q
What does the sympathetic nervous system do?
A
Dilates pupils
Inhibits salivation / digestion/contractions of bladder
Increases heart rate
Dilates bronchi
11
Q
What makes up the CNS?
A
Brain
Spinal cord
Brain stem
12
Q
What makes up the PNS?
A
31 pairs of spinal nerves
Motor neurones
Sensory neurons
Ganglion
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.
14
Q
How is information passed within neurones?
A
Electrically, from cell body to axon terminals via an action potential.
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.
16
Q
What are the 5 types of glial cells?
A
Schwann cells
Oligodendrocyte
Microglial cells
Ependymal cells
Astrocyte
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
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
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.
20
Q
What’s the function of the microglia?
A
- brains immune system - savage the CNS for plaque, damaged cells & infected agents
21
Q
What are ependymal Cells?
A
Make up the ependyma membrane lining of the central canal of spinal cord. They produce cerebrospinal fluid.
22
Q
What 3 parts make up the brainstem?
A
Medulla
Pons
Cerebellum
23
Q
Label the basic structures of the brain
A
Spinal cord
Brainstem
Midbrain
Thalamus
Basal ganglia
Cerebral cortex
24
Q
What does the medulla oblongata do?
A
Via chemoreceptors →
-Controls cardiac functions - heart rate & blood pressure
- respiration-breathing rate
- reflexes - vomiting, coughing
25
What does the pons do?
Contains nuclei that relay signals from forebrain to cerebellum - nuclei that deal with: sleep, respiration, swallowing, bladder control, hearing etc.
26
What does the cerebellum do?
Maintenance of balance & posture
Coordination of movements- across multiple joints
Motor learning
27
What does the midbrain do?
- 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
28
What does the thalamus do?
Takes info from periphery to the cortex
Hypothalamus - hormones, metabolic control eg. Body temp
29
What does the basal ganglia do?
A series of interconnected nuclei
- movement regulation, skill learning, habit formation, selection of appropriate behaviours
( programmed movements)
30
What does the cerebral cortex do?
Movement
Attention
perception
Awareness
Thought
Memory
Language
Consciousness
31
What is the spinal cord?
First point of call for info going into & out of the CNS
31
What is the spinal cord?
First point of call for info going into & out of the CNS
32
In the spinal cord is gray matter on the inside or outside ?
Inside, white matter on outside
33
Name the layers of the spinal cord?
Cervical (c)
Thoracic (t)
Lumbar (L)
Sacral (s)
34
What is gray matter?
Neurones & other cells
35
What is white matter?
Fibres that carry info up & down the cord.
36
Why is there less white matter in the lower sections of the spinal cord than in the cervical?
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.
37
Where is sensory info localised in the spinal cord?
The dorsal horn
- info such as fine touch, proprioception, pain & temp.
38
Where are motor neurons localised in the spinal cord?
The ventral horn ( bottom)
- these make direct contact with the muscles (effectors), stimulation of these neurons causes movement.
39
What is somatotopy?
Spatial map of the body. Eg. Adjacent neurons in neural tissue respond selectively to stimuli presented to adjacent locations on the body.
40
What are the 2 major descending systems of the spinal cord?
Lateral & medial descending systems.
41
What tracts make up the lateral descending system of the spinal cord?
Corticospinal tract (goes to cortex & comes from spine)
Rubrospinal tract
42
Where are fibres of the lateral descending system of the spinal cord found & where do they connect to?
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.
43
What do the corticospinal & rubrospinal tracts do?
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 .
44
What 2 tracts make up the medial descending system of the spinal cord ?
Vestibulospinal & reticulospinal tracts
45
Where are fibres of the medial descending system of the spinal cord found a where do they connect?
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.
46
What do the vestibulospinal & reticulospinal tracts do?
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.
47
What are the 2 major ascending pathways of the spinal cord?
Medial lemniscus (dorsal column pathway)
Spinothalamic tract (lateral spinothalamic tract)
48
What does the medial lemniscus (dorsal column pathway) do?
Carries sensory info from the joint & skin eg. Fine touch, vibration, two-point discrimination, & proprioception
49
What does the spinothalamic tract do?
Conveys crude touch- a sense of being touched without knowledge of where, pain & temperature.
50
Where do the cell bodies of incoming sensory neurones lie?
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.
51
How are the 31 pairs of spinal nerves divided?
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccyx
52
What does position of nerves determine?
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.
53
What are dermatomes ?
An area of skin supplied by nerves from a single spinal root.
54
What is 2-point discrimination?
The ability to discern that 2 nearby objects are being touched to the skin - this reflects how finely innervated an area of skin is.
55
What is a motor pool?
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.
56
What is a motor unit?
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.
57
What does the dorsal horn do?
Contains sensory neurones, these receive sensory info & send it up to the brain.
58
What does the ventral horn do?
Contains motor neurones that send messages directly to the muscles
59
What do motor neurones use to signal the amount of force to be exerted by a muscle ?
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
What is the name given to maximal contraction of muscles?
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
What does size & recruitment principle state about force and neurones?
With increasing strength of input onto motor neurones, smaller motor neurones are recruited & fire action potentials before larger motor neurones are recruited.
62
Describe the stretch reflex process?
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
What are reflexes?
Rapid automatic control of movement, with no voluntary control
Mainly happen in spinal cord & low in brain stem.
64
What are the 2 important brainstem nuclei groups?
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
What is the vestibular system of the brainstem?
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
What is the reticulospinal tract?
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
What is the superior cerebellar penduncle of the cerebellum?
Efferent (out) pathway of info to the cortex (through the thalamus) & to the red nucleus.
68
What is the middle cerebellar peduncle?
Most fibres originate in the pons, input from sensory, visual, vestibular & motor systems, input is from the cortext.
- Input
69
What is the inferior cerebellar penduncle?
Carries info to & from the spinal cord & vestibular nuclei
70
What is the red nucleus?
A spherical collection of cell bodies in the midbrain.it receives a large input from the cerebellum & primary motor cortex.
71
What are the 2 pathways in the basal ganglia?
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
What will happen if the basal ganglia is damaged?
States where there's too much or too little movement.
73
What will happen is the cerebellum gets damaged?
States where movement can still be made, but they are uncoordinated.
Actions are hesitant & clumsy, & affects balance & gait.
74
What is the cerebral hemisphere?
Outer surface of brain, superficially divided into several lobes which are responsible for higher reasoning.
75
What is the function of the cerebellum?
Base of brain, important for timing, planning of movement, motor memory & posture & executing motor skills.
( co-ordinated movement).
76
What is the alternative name for forebrain?
Prosencephalon
77
What is the alternative name for mesencephalon?
Midbrain
78
What is the alternative name for rhombencephalon?
- Hindbrain
79
What are the 3 ancestral regions of the vertebrate brain?
- Forebrain (prosencephalon)
- midbrain (mesencephalon)
- hindbrain (rhombencephalon)
80
By the 5th week of development what does the forebrain (prosencephalon) divide into ?
- Endbrain (telencephalon)
- interbrain (diencephalon)
81
By the 5th week of development what does the hindbrain (rhombencephalon) constrict to form?
- Afterbrain ( metencephalon )
- the spinal brain ( myelencephalon)
82
What makes up the telencephalon?
The cerebrum
83
What makes up the diencephalon?
The thalamus, hypothalamus, & epithalamus
84
What makes up the mesencephalon?
The midbrain (brainstem)
85
What makes up the mesencephalon?
Pons (brainstem)
Cerebellum
86
What makes up the myelencephalon?
Medulla oblongata (brainstem)
87
What does the diencephalon do?
- 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
Function of thalamus
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
Function of the hypothalamus
Homeostasis - autonomic control centre, regulation of body temp, food intake, water balance, sleep-wake cycles & control of endocrine system functioning.
90
Function of subthalamus
Subthalamic nucleus has a role in processing that occurs in the basal ganglia.- unknown
91
Function of epithalamus
Relay station between the senses & the cerebral cortex. The pineal gland is part of the epithalamus.
92
What is the midbrain?
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
Are dorsal roots efferent or afferent?
Dorsal roots are afferent, so carry sensory info to the CNS from the PNS
94
Are ventral roots efferent or afferent?
Ventral roots are efferent, so carry motor info from the CNS to the PNS
95
What is the dorsal root ganglion ?
Part of the dorsal root that contains the cell bodies of the sensory nerve fibres.
96
What is the spinal nerve?
Dorsal & ventral roots joint to from a spinal nerve, which is a mixed nerve as it carries both sensory & motor neurons.
97
How many pairs of spinal nerves do humans have ?
31 pairs
98
Where do motor neurone cell bodies reside?
In the spinal cord.
99
What do each spinal nerve divide into ?
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
What is a plexus ?
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
What is the corticospinal tract?
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
What is upper motor neurone syndrome ?
Damage to the corticospinal tract causes dysfunction in the motor control of skeletal muscles resulting in paralysis, tenseness, spasticity, weakness, muscle twitches & spasms
103
Which way do dermatomes run on the trunk?
Honzontally.
104
Which way do dermatomes run along the arms & legs?
Vertically
105
What is the corpus callosum ?
Large bundle of neuronal axons passing between the left & right hemispheres that allow communication between the two hemispheres.
106
What is the cerebral cortex?
Composes outer layer (grey matter) of brain, involved in higher brain functioning , like reasoning, abstract thought & language.
107
What does the frontal lobe do?
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
What does the parietal lobe do?
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
What does the occipital lobe do?
Contains visual cortex, primary visual cortex contains a well defined map of visual info received from the outside world.
110
What does the temporal lobe do?
Contains auditory cortex which receives & processes auditory info.
Wernicke’s area is involved in language comprehension.
111
What happens in the primary motor cortex?
Neurones fire around 5-100 Ms before movement onset & can code for the basic parameter for movement. Eg. Force, speed.
112
What happens in the pre-motor cortex?
Neurones code for more complex parameters of movement eg. Spatial & sensory guidance movement
113
What happens in the supplementary motor cortex ?
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
What happens in the primary sensory cortex ?
Touch-vibration, heat, pain, pressure,proprioception eg joint position sense.
115
What happens in posterior parietal cortex ?
Integration of sensory, visual info to execute complex movement in the environment.
116
What is an autocrine signal?
Can be signalled by the same cell
117
Paracrine signal
Signalled by nearby cells, via cytokines.
118
Signal via distant multi- cellular organisms.
Endocrine signalling by hormones
119
What are the types of cell signals?
Hormones, chemical element eg. Protein, light, heat, water.
120
What can signalling systems do?
- warn off pathogens infections.
- alter / regulate metabolic processes
-Switch on or off feedback loops.
121
What response does cell signalling have?
-Change in metabolism of cell
- change in electrical charge of csm
- change in gene expression of cell.
122
- What are Exocrine glands?
Secrete their products into ducts ( sweat/intestines)
123
What are endocrine glands?
Ductless, they release hormones into the blood.
124
What are hormones?
Chemical messengers carried by the blood to target cells.
125
Why are hormones specific?
They only affect specific target cells, with receptors for that hormone.
126
What is the function of hormones?
- 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
What is the difference between the endocrine & the nervous system?
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
What are the 3 major structural classes of hormones?
- Amines eg. Thyroid Hormones, dopamine
- peptides & proteins eg. Insulin
- steroids eg. Cortisol, androgens (testosterone)
129
Are peptide hormones soluble?
Yes, peptides & all catecholamine hormones are water soluble - therefore, circulate dissolved in the plasma. Some bind to plasma proteins.
130
Are steroid & amine hormones soluble ?
No, they circulate mainly bound to plasma proteins.
131
What are the major organs that remove hormones from the plasma?
Liver & kidneys by metabolizing or excreting them.
132
What is the mechanism of hormone action?
Transport via blood to target tissue - receptors for hormones on or in target cells.
133
Where are receptors for steroid & thyroid hormones (amine) found ?
Inside target cells ( lipid soluble)
134
Where are receptors for peptide hormones & Catecholamine's found?
On the plasma membrane
135
What does the responsiveness of a target cell to a hormone depend on ?
- 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
What is hormone secretion controlled by?
- 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
Motor neurons that control the upper limbs are found in which part of the spinal cord?
Cervical enlargement
138
Which protein blocks the actin binding site during the cross-bridge cycle?
Tropomyosin
139
The brain consumes roughly, how much of the human body's cardiac output?
10 - 19%
140
Which hormones are released from the anterior pituitary gland?
Follicle stimulating hormone
Growth hormone
Thyroid stimulating hormone
Adrenocorticotropic hormone
141
What is the supplemental motor area involved in?
Bimanual coordination
142
Which part of the feedback system receives afferent into from the regulated variable & sends a signal to the control centre?
Sensor
143
Is skeletal muscle multinucleated & does it have a single or double neuromuscular junction per fibre?
- Skeletal muscle is multinucleated & has a single neuromuscular junction per fibre.
144
Can a single fibre be innovated by 2 or more motor neurons?
No it cannot
145
Can muscles contain motor units of different sizes?
Yes many muscles do
146
Are the biggest motor units the fastest & most fatigable?
Yes
147
What are changes in mean arterial pressure sensed by?
Mechanoreceptors in the carotid sinus & aorta arch, this afferent info is processed in the medulla.
