The Brain

Question 1

Mid Brain

Answer 1

Tectum: controls orientation of head and neck, also contains the substantial nagar associated with sleep and wake cycles and thermoregulation

Question 2

Forebrain

Answer 2

Thalamus: switchboard, takes info from peripheral and passes to cortex - hypothalamus (regulate hormones and metabolic control)
Basal Ganglia: is a series of interconnected nuclei, involve skill learning, habit formation,reward system, and self behaviour.
Cerebral cortex: controls movement,attention awareness thought,memory and language

Question 3

Brain stem

Answer 3

Medulla: controls cardiac functions, respiratory functions, and reflexes.
Pons: contains nuclei that relays signals from forebrain to cerebellum, nuclei that deal with sleep,respiration, swallowing, taste, sensation and posture.
Cerebellum: maintains balance and posture, helps co ordinate movements and motor learning.

Question 4

Cortex breakdown

Answer 4

Frontal lobe: Motor cortex (speech)
Parietal lobe: somatosensory cortex ( taste,speech,reading)
Occipital lobe: visual cortex (vision)
Temporal lobe: auditory cortex ( hearing)

Question 5

Counting Brain cells

Answer 5

Collecting segments of each part of brain and dissolving the cells and surrounding structure - leaving each nuclei whole (nuclei suspension)
Nuclei are isotopic cells (same value in different directions).
Seperate the DNA cells from the neuronal cells .

Question 6

Brain energy consumption

Answer 6

Brain in energy hungry :
Alone brain consumes 20% of bodies energy, due to 15-20% of cardiac output directed to the brain
Flurodeoxyglucouse is a marker for glucose uptake and shows at rest majority of glucose in brain for energy production.
Through time shows once meat was consumed brain grew.

Question 7

Reflexes

Answer 7

Reflexes are involuntary and unplanned sequences or action
They’re nearly instantaneous movement in response to a stimulus
Actions occur before presence can reach the brain
Automatic response to a stimulus that does not receive conscious though

Question 8

Spinal reflex

Answer 8

Spinal reflexes:
Stereotyped movement s excited by the activation of skin or muscle receptors.
Complex sequences of movement and be produced by combining reflexes eg.walking
They can exist without a brain eg.brain damage

Question 9

Stretch reflexe

Answer 9

Stretch reflex:
Monosynaptic ans disynapric components involved.
Large sensory fibres are coiled around a muscle spindle, and the stretch of muscle is detected by these.
This imitates action potentials in sensory nerves to spinal cord
These synapses with motor neurons, innervate with same muscle that’s contracting ..
So sensory neurons activate inhibitory connections of antagonistic muscle, working against the force.

Question 10

Stretch reflex sequence

Answer 10

1. Disruption in load on muscle
2. Length change in muscle fibre
3. Signals reach muscle spindles, and they increase afferent discharge
4. Information sent to motor neurons deciding facilitation or inhibition to the muscle
5. When signals reach the muscle, tells muscle to react to prevent overworking muscle and injury

Question 11

Withdrawal reflex

Answer 11

Withdrawal reflex:
A quick contraction of flexor muscles resulting in withdrawal of limb, usually response to painful stimuli.
Required coordination movement of limbs.
It’s a polysynaptic reflex arc.
Pain receptors stimulated, sensory neurons activate multiple inter neurons, then ipsilateral motor neurons to flexor excited, and contracts.

Question 12

Withdrawal reflex sequence

Answer 12

1. Pain receptors pick up on stimului
2. Sensory neurones receive signals
3. Motor neurones flex the ipsilateral muscles
4. Ipsilateral muscles contact to respond away from the pain stimuli
5. Motor neurones also flex the contralateral extensor

Question 13

Sensorimotor

Answer 13

Sensorimotor: Most movements in response to outside stimuli, simplest are quick,stereotyped and rapid.

Question 14

Spinal cord makeup

Answer 14

The middle cord is made up of neurones and other cells (grey matter)
Outside cord is made up of the fibres( white matter) that carry information up and down the the cord covered by myelin to protect at insure fast movement of neurones.
The dorsal horn is where sensory information comes into the spinal cord , involves information about touch,proprioception, vibration,pain and temperature
The ventral horn is where the Motor neurones are located, they make direct contact onto muscles and stimulation of these causes movement, each cell is part of a Motor unit.

Question 15

Motor units

Answer 15

Motor units make up motor pools, a lower motor neurone in spinal cord innervates a muscle.
Each motor neuron synapses with multiple fibres within the muscle.
The motor neurone and muscle fibres it contacts makes up the motor unit.
Their is a wide distribution of muscle fibres contacted by a motor neurone.

Question 16

Spinal cord makeup

Answer 16

Cervical
Thoracic
Lumbar
Sacral

Question 17

Lateral descending system

Answer 17

2 parts: cortical and rubrospinal
They are the lateral part of spinal cord , and connect motor neurones to lateral part of ventral horn, influencing lateral musculature.
Corticospinal fibres are strongly influenced movement of every part of the body and is particularly useful for individual finger use
Other descending fibres, primarily rubrospinal tract can compensate almost complete for loss of corticospinal input.
The one unique factor of corticospinal tract is the ability to use the fingers individually.

Question 18

Medial descending system

Answer 18

2 parts: vestibulospinal and reticulospinal
The fibres are found in the ventro medial white matter, connecting motor neurones to medial ventral horn, influences medial musculature
They are involved in balance and posture, with little conscious control
The vestibulospinal tract retains balance when body is moved, with external disturbance.
The reticulospinal tract helps retain posture and balance during volitional movements , with internal disturbance

Question 19

Ascending systems

Answer 19

Dorsal column pathway: carries sensory information from joints and skin about fine touch, vibration, two point discrimination and proprioception.
Spinothalamic pathway: conveys information about crude touch (sense of being touched without knowledge of where), pain and temperature.

Question 20

Dorsal root ganglion

Answer 20

The cell bodies of incoming sensory neurones lying outside of the spinal in a series of ganglion is called :
Dorsal root ganglion

Question 21

Spinal nerves

Answer 21

31 pairs of Spinal nerves
The positions in the spines these are determines what part of the body each spinal nerve serves.
As many parts of body have more muscles and more sensory receptors , the size of the nerve and the amount of information carried by the nerve will be different in each.
Dermatomes: are areas Of the skin supplied by nerves from a single spinal root.

Question 22

Spinal enlargement

Answer 22

Spinal enlargement:
The arms and legs have many innervated muscles and have a high density of sensory receptors.
Because Of this the portions of the spinal cord that provide the spinal nerves to arms and legs are enlarged.

Question 23

Spinal nerves innervates

Answer 23

Cervical - shoulders and arms
Thoracic - abdominal
Lumbar - legs
Sacral- lateral side of feet and reproductive organs

Question 24

Information flow in spinal segment

Answer 24

Dorsal horn contains sensory neurones, these recieve sensory information and send this up to the brain.
Ventral horn contains neurones that send messages directly to the brain
Intermediate zone contains inter neurones these integrate information eg.inhibition

Question 25

Coding in the sensory system

Answer 25

Coding in the sensory system: Stimulus intensity determines the size of receptor potential and thus frequency of action potentials. Firing frequency codes for intensity “rate code” very non linear usually codes for intensity of contrast between two levels.

Question 26

Coding in motor system

Answer 26

Coding in the motor system Motor neurones use a rate code to signal the amount of force to be exerted by a muscle. An increase in the rate of action potentials fired by motor neurone causes an increase in amount of force a motor unit generates. Single action potentials will produce a single twitch. Multiple potentials occur in succession the force of muscle builds up. At a certain rate the muscle will be unable to contract further - max contraction. This called titanic contractions and occur when input at frequency is so fast muscle can’t relax between potentials

Question 27

Recruitment principle vs size principles

Answer 27

Recruitment principle - small forces recruit small motor units and as force increases larger motor units are recruited Size principle - states that increasing strength of input onto motor neurones, smaller neurones are recruited and fire before larger motor neurones.

Question 28

Basic layout of subcortical motor system

Answer 28

Basic layout of subcortical motor system: Spinal cord Medulla Pons Cerebellum Midbrain Thalamus Basal ganglia

Question 29

Stretching muscle …

Answer 29

Stretching a muscle is detected in the muscle and leads to increase activity in sensory neurones that in turn leads to an increase in activity of motor neurones that innervate the same muscle, while inhibiting motor neurones that innervate antagonists.

Question 30

2 Important brainstem nuclei groups

Answer 30

Vestibular tract: sensory system that provides sense of balance and spatial orientation for the purpose of coordinating movement with balance. It originates in vestibular nuclei, sending most of output to spinal cord and muscles that move the eyes. Recticulospinal tract: set of interconne nuclei located throughout brain stem, originates in reticular formation and maintains tone, balance and posture.

Question 31

Superior cerebral peduncle? Middle cerebral penduncle? Inferior cerebral penduncle?

Answer 31

Superior cerebral peduncle: efferent pathway to the red nucleus and the cortex and sup colliculus. Middle cerebral penduncle: originate in pons input from sensory,visual vestibular and motor systems. Inferior cerebral peduncle: carries infor from spinal cord and vestibula nuclei.

Question 32

Red nucleus

Answer 32

Red nucleus is a spherical collection of cell bodies in mid-brain, receives large input from cerebellum and primary motor cortex it includes the rubrospinal tract: The fibres originate in the red nucleus, after exiting nucleus. They occupy white matter , determining in cervical and lumbar of the cord controlling shaping of the hand

Question 33

Basal ganglia

Answer 33

Basal ganglia: Controls movement regulation, skill learning, habit formation and reward systems. Selects appropriate behaviour and self initiation of behaviours.

Question 34

Basal ganglia pathways

Answer 34

2 pathways: Direct ( short loop through basal ganglia, has excitatory effect on cortex, and is pro movement) Indirect ( long loop through basal ganglia, has inhibitory effect on cortex and is anti movement movement

Question 35

Brain maps

Answer 35

Brain maps Primary sensory and motor cortex have detailed somatopic maps of the body in them. Areas of the body with many highly innervated muscles and densely packed sensory receptors have expanded representations in the brain

Question 36

Several motor areas In cortex

Answer 36

Several motor areas in cortex: Primary motor cortex:: neurones in the primary motor cortex have relationships to movement. They fire around 5 to 100 before movement onset and can code for basic movement ( force,direction,extent,speed) Non primary motor cortex: more complex relationship to movement, coding for the complex aspects of movement. Examples are: Pre motor cortex: useful in planning movement, spatial guidance and sensory guidance of movement Supplementary motor cortex: in charge for coordination of temporal sequencing, bimanual coordination, initiation of internally generated..

Question 37

Areas associated with movement

Answer 37

Areas closely associated with movement: Primary sensory cortex: controls touch,vibration,heat pressure. Also control proprioception about information on joint position (recognition of joint position), kinaesthesia ( ability to recognise joint ,movement or control), and sensation or resistance ( recognition of force generated) Posterior parietal cortex: intergrates sensory, visual infor to complex movement, representing for different motor effectors.

Question 38

Corticospinal tract

Answer 38

Corticospinal tract For precise control of the limbs Origin is primary motor cortex(30%), pre motor,supplementary(30%), somatosensory parietal and Cingulate (40%)