Physiology

Question 1

What is syncope?

Answer 1

Syncope is the key feature is a transient loss of consciousness and common pathophysiologic mechanism that includes a cerebral hypoperfusion.

Question 2

What are requirements for consciousness?

Answer 2

1. Adequate perfusion of brain with oxygenated blood
2. Adequate delivery of glucose
3. Adequate neural activity

Question 3

What are some of the causes of syncopal collapse?

Answer 3

1. Situational - pain stress and other
2. Reflex - vasovagal syncope
3. Cardiac - arrhythmia and bradycardia
4. Psychogenic - anxiety disorders, depressive disorders
5. Metabolic/other - hypoglycemia
6. Neurologic - seizures

Question 4

What is the cause of reflex and neurally mediated syncope?

Answer 4

The transient shift in autonomy response tends to trigger vasodilation which reduces cardiac output. This cause a drop in blood pressure which reduces peripheral perfusion.

Question 5

What is the cause of situational syncope?

Answer 5

Compression of the vena cava, reduced venous return reduced cardiac filling, reduced cardiac output and a decrease in blood pressure. This increase SNS output. When breathing is resumed – the venous system improves cardiac filing, above normal resulting in transient increase in blood pressure. This increases parasympathetic drive. Bradycardia occurs which reduces blood pressure hence decreased cerebral pefusion/syncope

Question 6

What is the Non-syncopal TLOCs?

Answer 6

The term Transient Loss of Consciousness is sometimes used when the cause is either unrelated to cerebral hypoperfusion or is unknown

Question 7

What is the cause of syncope in psychiatric disease?

Answer 7

Hyperventilation, leads to hypocapnia, causing a transient increase in cerebrovascular resistance coupled with simultaneous peripheral vasodilation

Question 8

What is the relation between dizziness & TLOC in pregnancy?

Answer 8

Progesterone promotes vasodilation – systolic bp can decrease – increase the likelihood of orthostatic hypotension

Question 9

What are the functions of insulin?

Answer 9

1. Insulin promotes uptake of glucose into muscle and adipose tissue
2. Insulin promotes fat and glycogen synthesis in the liver from acetyl CoA. Fat is sent to the adipose tissue for storage.

Question 10

What is the mechanism of action of insulin?

Answer 10

1. It binds to extracellular tyrosine kinase receptor
2. Activation of protein kinase B occurs
3. Cellular response leads to: anabolic pathway activation, catabolic pathway inactivation
4. Modulation of gene expression
5. Recruitment/translocation of insulin-regulatable transporters from cytoplasm to the cell membrane

Question 11

What are the three types of movements humans can produce?

Answer 11

1. Reflective - involuntary coordinated patterns of muscle contraction
2. Rhythmic - repetitive rhythmic motor patterns e.g. chewing
3. Voluntary contractions – actions generated by the cerebral cortex

Question 12

What are the steps in a simple reflex arc?

Answer 12

1. Receptors
2. Sensory neuron
3. Integraton centre
4. Motor neuron
5. Effector muscle

Question 13

What are the two main sensory receptors in the muscles?

Answer 13

1. Muscle spindle – capable of detecting changes in muscle length and rate of change in length
2. Tendon organs – capable of detecting changes in muscle force

Question 14

Explain the tendon tap reflex.

Answer 14

1. The tendon in the knee is struck
2. This cause the stretch of the quadriceps
3. The stretch is detected by the muscle spindle
4. The afferent signal is propagated to the spinal cord
5. An efferent signal is send from the spinal cord to the effector muscle
6. This causes muscle contraction
7. Result - leg jerks forward

Question 15

What is the main purpose of the golgi tendon organ?

Answer 15

It is to protect the muscle from injury due to sudden or excessive load. They reside on the junction between the muscle and the tendon and are able to used inhibition signals to protect the muscles

Question 16

Explain the flexor withdrawal reflex?

Answer 16

1. A painful stimulus is detected
2. It travels via the afferent neuron to the spinal cord
3. Excitation of flexor and inhibition of extensor muscles occur via efferent neurons
4. Result - the limb is removed from the pain stimulus

Question 17

Explain the crossed extensor reflex.

Answer 17

During the flexor withdrawal reflex, a contralateral extensor needs to occur to create balance. This means inhibition of flexor and excitation of extensor will occur on the opposite side of the body.

Question 18

What is an interesting fact about muscle spindles and mastication?

Answer 18

Muscle spindles are mostly present in the jaw opening muscle and least present in the jaw closing muscles. This makes sure that chewing is regulated and you be able to chew through hard objects and your jaw does not bounce during jogging.

Question 19

What is an interesting fact about golgi tendon organs and mastication?

Answer 19

They are present in the muscles of mastication – but their role is unclear!

Question 20

Explain the periodontal reflexes (sharp tap).

Answer 20

1. Periodontal mechanoreceptors sense a hard tap on the tooth
2. An afferent excitatory signal is send
3. An inhibitory efferent signal is sent to the closer muscle
4. Result - the jaw will not close

Question 21

Explain the periodontal reflexes (smooth tap).

Answer 21

1. Periodontal mechanoreceptors sense a smooth tap on the tooth
2. An afferent excitatory signal is send
3. An excitatory signal is send to the closer muscles
4. Result - the jaw closes to keep the food in

Question 22

What is proprioception?

Answer 22

It is the awareness of the sense of position of body segments in space, whereas kinaesthesia is the sense of movement.

Question 23

What are the 4 types of primary afferent axons and what are their function?

Answer 23

1. A-alpha – thickest – at proprioceptors of skeletal muscles
2. A-beta – thicker – at mechanoreceptors of skin
3. A-delta – thick – used at the receptors that detect pain and temperature
4. C - thin – use at the receptors that detect temperature, pain and itch

Question 24

What is a sensory unit?

Answer 24

It is a single primary axon with it’s correlating sensory units

Question 25

In terms of coding of sensory stimuli, what are the three things we must know?

Answer 25

1. Modality - type of stimulus 2. Intensity - how big the stimulus is 3. Location - where the stimulus is

Question 26

Which of the skin receptors have large receptor fields?

Answer 26

Deep receptors have large receptor fields – such receptors are pacinian corpuscle and ruffini end organs Superficial receptors have smaller receptor field – such receptors are merkel discs and meissnes corpuscles

Question 27

What are the more important receptors for proprioception?

Answer 27

The deep receptors with large sensory fields as they are able to be activated during joint movements

Question 28

What is important to understand in regards to proprioception and receptor cooperation?

Answer 28

The best outcomes in terms of proprioception occur when all receptor can contribute

Question 29

How does the proprioceptive information carried to the appropriate processing center in the brain?

Answer 29

Proprioceptive information is carried to the somatosensory cortex mainly via dorsal column-medial lemniscal pathway. This means that a primary afferent exon carries the information to and up the spinal cord, then synapsis occurs and the secondary axon carries the information through the opposite side to the thalamus. At the thalamus another synapses occurs and the tertiary axon carries the information to the somatosensory cortex

Question 30

What is a 2 point discrimination?

Answer 30

It is a process where 2 different stimuli are presented on the surface of the skin and are move closer and closer together until the individual can longer differentiate the two points, rather they think that the point is one. 2 point discrimination varies largely throughout the body.

Question 31

What is the relationship between the proprioception and the teeth?

Answer 31

Each tooth has a large number of periodontal mechanoreceptors. This mechanoreceptors are able to sense and signal when certain pressures are applied on the teeth. Which means the proprioception in regards to the jaws can occur as well as reception of objects between the teeth. The proprioception in the jaws is very very sensitive.

Question 32

What is the difference between the proprioception between people with and without dentures?

Answer 32

People with dentures usually lack the periodontal mechanoreceptors meaning they have an altered sensation of objects in the mouth. Also they, dentures usually cover oral mucosa, which further impairs the perception of intra oral forces. Furthermore, considerable motor learning may be required to adapt to use of dentures for speech and mastication

Question 33

What is a motor unit?

Answer 33

It is the functional unit of the muscle that signals for muscle activation. It has a variable area of action depending on the size of the single motor unit and the amount. Large motor units on large muscles are able to effect large muscle while small motor units can affect the eyes.

Question 34

What are the three types of motor units?

Answer 34

1. Slow twitch (type I) - are slow twitch, low force and fatigue resistant – mostly present in masseter muscle for example – tbh in nearly all muscle of mastication 2. Fast twitch-fatigue resistant (type II a) - are fast twitch, moderate force, fatigue resistant 3. Fast twitch (type II b) - are fast twitch, high force, fast fatigue

Question 35

What are the two ways we can increase force in the muscle?

Answer 35

1. Recruitment - involvement of new motor neurons | 2. Rate of coding – increase in frequency of action potential discharge

Question 36

What is the hierarchy of motor control?

Answer 36

1. Highest level – planning – development of strategies and motor plans to achieve the goal – cortical association areas, basal ganglia, cerebellum 2. Middle level – commanding – integration of signals from higher areas to deliver specific commands – motor cortex and brainstem descending pathways 3. Lowest level – execution – integration of sensory afferent and descending pathways – spinal interneurons and motoneurons

Question 37

What is mastication?

Answer 37

It is a rhythmic activation of jaw muscles in a highly coordinated manner. It requires constant conscious effort and monitoring not required.