BMA End of Semester Test

Week 7 - Week 10

Cranial Nerve I - Name

Olfactory Nerve

Cranial Nerve I - Function

Conducts sensory input for olfaction

Cranial Nerve II - Name

Optic Nerve

Cranial Nerve II - Function

Conducts sensory input for vision

Cranial Nerve III - Name

Oculomotor Nerve

Cranial Nerve III - Function

Conducts motor output for:

• The movement of the eyeball

• Constriction of the pupils

• Changes in lens shape

Cranial Nerve IV - Name

Trochlear Nerve

Cranial Nerve IV - Function

Conducts motor output for eyeball movements

Cranial Nerve V - Name

Trigeminal nerve

Cranial Nerve V - Function

• Conducts sensory input for pain, touch and temperature from the face

• Conducts motor output to the muscles involved in mastication (chewing)

Cranial Nerve VI - Name

Abducens nerve

Cranial Nerve VI - Function

Conducts motor output for eyeball movement (abduction)

Cranial Nerve VII - Name

Facial nerve

Cranial Nerve VII - Function

• Conducts sensory input for taste

• Carries motor output for facial expression, salivation and tears

Cranial Nerve VIII - Name

Vestibulocochlear nerve

Cranial Nerve VIII - Function

Conducts sensory input for hearing and balance

Cranial Nerve IX - Name

Glossopharyngeal nerve

Cranial Nerve IX - Function

• Conducts sensory input for taste

• Carries motor output for movements of pharynx (swallowing, speech) and salivation

Cranial Nerve X - Name

Vagus nerve

Cranial Nerve X - Function

• Conducts sensory input for taste, proprioception (pharynx), blood pressure, blood gasses, visceral sensations

• Conducts motor output for swallowing, breathing, cardiac function, digestive activities

Cranial Nerve XI - Name

Accessory nerve

Cranial Nerve XI - Function

Conducts motor output for movements of head, neck and shoulders

Cranial Nerve XII - Name

Hypoglossal nerve

Cranial Nerve XII - Function

Conducts motor output for tongue movements (swallowing and speech)

Fasciculus gracilis and fasciculus cunteatus tracts

• Location

• Conducted information

Posterior white columns

Fine touch, vibration, light pressure and conscious proprioception

Posterior column pathway

• First-order neurons conduct sensory input from proprioceptors and tactile receptors into the spinal cord and to the medulla oblongata

  • Ascend in a fasciculus gracilis or fasciculus cuneatus tract (each does one side of the body)

  • Within the medulla oblongata the first-order neuron synapses with and passes information on to a second-order neuron

• Second-order neuron conducts information up the brain stem and to the thalamus

• Third-order neuron carries the information from the thalamus and to the primary somatosensory cortex

Anterior spinothalamic tract

• Location

• Conducted information

Anterior white columns
Crude touch and deep pressure

Lateral spinothalamic tract

• Location

• Conducted information

Lateral white columns

Pain and temperature

Spinothalamic pathway

• First-order neurons conduct the sensory input detected by thermoreceptors, nociceptors or tactile receptors into the spinal cord

  • The sensory information is delivered to the posterior gray horn and within a sensory nucleus the first-order neuron will synapse with and pass the information onto a second-order neuron

• Second-order neuron decussates and conducts the sensory information through the spinal cord and brain stem to the thalamus

  • If they are conducting pain or temperature information they will be located in a lateral spinothalamic tract

  • If they are conducting crude touch or deep pressure information they will be located in an anterior spinothalamic tract

• Third-order neurons conduct the sensory information from the thalamus to the primary somatosensory cortex

Anterior and posterior spinocerebellar tracts

• Location

• Conducted information

Lateral white columns

Unconscious proprioception, helps to maintain smooth muscle movements and balance and posture

Spinocerebellar pathway

• First-order neurons conduct sensory information into a posterior gray horn within a sensory nucleus and synapses with and passes the information onto a second-order neuron

• Second-order neuron conducts the information to the cerebellum via a posterior or anterior spinocerebellar tract

Lateral corticospinal tracts

Lateral white columns

Somatic motor output that controls the skeletal muscles of the limbs

Lateral corticospinal pathway

• Upper motor neurons, located in the primary motor cortex generate the somatic motor output that stimulates your skeletal muscles to contract

• The axons conduct the information down the brain stem and the spinal cord through the lateral corticospinal tract

• Within a nucleus of an anterior gray horn the upper motor neuron synapses with and passes the information onto a lower motor neuron

• Lower motor neuron conducts the information away from the spinal cord to the skeletal muscle of a limb

Anterior corticospinal tracts

Anterior white columns

Somatic motor output that controls the skeletal muscles of the trunk/axial skeleton

Anterior corticospinal pathway

• Upper motor neurons, located in the primary motor cortex generate the somatic motor output that stimulates your skeletal muscles to contract

• The axons conduct the information down the brain stem and the spinal cord through the anterior corticospinal tract

• Within a nucleus of an anterior gray horn the upper motor neuron synapses with and passes the information onto a lower motor neuron

• Lower motor neuron conducts the information away from the spinal cord to the skeletal muscle of the trunk

Purpose of somatic reflexes

• Produced by the grey matter of the spinal cord

• Since the reflex response is always the same, somatic reflexes are often tested to quickly diagnose disorder of the nervous system

• Injuries or disease that affect the spinal cord segments that mediate the response of lower motor neurons can result in loss of reflex activity

• Brain injuries that affect the primary motor cortex and corticospinal tract can result in abnormal reflexes

Examples of somatic reflexes

Babinski sign

Indicates damage to the primary motor cortex or corticospinal tracts

Spinal cord injuries

Damage to the posterior gray or ascending spinal cord tracts  located in the posterior, lateral and anterior white columns can result in a loss of sensation

What is spastic paralysis?

Occurs when a spinal cord injury damages upper motor neurons where the somatic motor output generated by the primary motor cortex, will not be conducted down the spinal cord to lower motor neurons and therefore skeletal muscles will not be stimulated to contract voluntarily

*Reflex integration centres have not been affected within the spinal cord or lower motor neurons which

What is flaccid paralysis?

Occurs when a spinal cord injury damages lower motor neurons where somatic motor output will not be conducted away from the spinal cord to skeletal muscles and therefore our muscles will not be stimulated to contract through reflex activity

*Loss in voluntary muscle movements and reflex activity which will result in abnormal reflex response due to the primary motor cortex can no longer influence the reflex response

A complete transection of the spinal cord

• Transection in the cervical region all four limbs are affected, known as quadriplegia

• Transection in the thoracic or lumber region both legs will be affected, known as paraplegia

  • If it occurs in the thoracic region, patients will need a manual wheelchair as all leg muscles are affected

  • If it occurs in the lumber region, patients may require assistive devices (e.g. leg braces and crutches) as not all leg muscles are affected

• Providing there is no damage to the reflex centres or lower motor neurons below the level of the transection, reflex activity will be present but abnormal as the primary motor cortex is unable to influence the reflex response

Sympathetic NS functions

• Blood vessels

• Lungs

• Liver

• Salivary glands

• Kidney

• Spleen

• Blood vessels, vasodilation to increase blood flow

• Lungs, bronchiole dilation

• Liver, stimulates glucose into blood

• Salivary glands, stimulates secretion of thick saliva

• Kidney, reduced blood flow and urine formation

• Spleen, release of stored blood

Parasympathetic NS functions

• Heart

• Liver

Heart, blood pressure decreases

Liver, increases glucose uptake

What organs do not have dual innovation, and only apply to the sympathetic NS?

Blood vessels, sweat glands, adrenal gland and spleen

Somatic NS vs Autonomic NS Overview

Somatic pathway and neurotransmitters

• Lower motor neuron releases ACh

• Skeletal muscles have cholinergic, nicotinic receptors

Sympathetic NS pathway and neurotransmitter

• Preganglionic neuron is short and it releases ACh which binds to the postganglionic neuron which is an excitatory response

• Postganglionic has a cholinergic, nicotinic receptor type and it releases NA and is long

• Targets are cardiac muscles, smooth muscles and glands muscles which have adrenergic (alpha or beta subtype) which have either an inhibitory or excitatory response

Parasympathetic NS pathway and neurotransmitter

• Preganglionic neuron is long and it releases ACh which binds to the postganglionic neuron which is an excitatory response

• Postganglionic has a cholinergic, nicotinic receptor type and it releases ACh and is short

• Targets are cardiac muscles, smooth muscles and glands muscles which have cholinergic (muscarinic subtype) which have either an inhibitory or excitatory response

Subtypes of cholinergic receptors

1. Nicotinic, also bind nicotine and are always excitatory

   • Leads to an action potential which increases the activity of the target

   • Found in the cell bodies of the postganglionic neurons in the synapse

   • When Ach is released by the sympathetic preganglionic neuron this innervates these cells this excites the cells to release adrenaline and noradrenaline into the blood

   • When the lower motor neuron releases ACh it binds to skeletal muscles which leads to action potentials that increase muscle activity

2. Muscarinic, also bind muscarine that comes from mushrooms

   • Mostly excitatory

   • Some of them are inhibitory which means it makes the action potential less likely which reduces the activity of the target

   • Receptors on cardiac muscle are inhibitory which reduces the likelihood of the action potential and overall decreases the activity of the heart

Subtypes of adrenergic receptors

1. Alpha receptors, two types of alpha receptors

   • A1, when A or NA bind this will increase the activity of the target which is going to cause smooth muscle in blood vessels to constrict and visceral organs sphincters, dilates pupils 

2. Beta receptors, three types of beta receptors

   • B1, when noradrenaline or adrenaline bind this increases the activity of the heart and increases blood flow

   • B2, found on smooth muscles and are inhibitory so when the NA or A bind this decreases the activity which relaxes the smooth muscle that is present in airways

Adrenergic receptor drugs

Acetylcholine (ACh)

• In the CNS

• Low levels of this neurotransmitter are found in individuals with dementia, especially Alzheimer’s disease

• This is where there is a loss of neurons particularly in the prefrontal cortex and in the hippocampus which produces problems in cognition and memory

Noradrenaline

Stimulates the reward and pleasure centres in the brain and helps to see rewards and take actions to move towards those rewards ("feel good" NT)

• Involved in reducing stress and enhancing attention

Dopamine

Associated with addiction which is released during pleasurable activities, therefore this NT reinforces those behaviours and helps promote addition

• People with schizophrenia (a disorder that affects a person's ability to think, feel and behave clearly) have high levels of dopamine

• Deficient in people with Parkinson's disease as this NT is responsible for controlling the basal nuclei which is important for helping us with the fine control of our motor activity

Serotonin

Involved in regulating mood, sleep, appetite and it can be associated with nausea and migraine

• Drugs that prevent the re-uptake of serotonin are thought to help with conditions like anxiety and depression as they reduce the activity of the amygdala, which means a person becomes less emotionally reactive

• Dark chocolate stimulates the release of serotonin in the brain and that’s why its thought to have a natural antidepressant kind of effect

Substance P

Produced in the periphery by damaged tissue

• It stimulates local nociceptors so we can transmits pain to the CNS

Endorphins

Inhibit our perception of pain

• A group of chemicals that involve endorphins and enkephalins

• Termed "natural opiates" as they are chemically similar to opiate drugs

• Also induce sleepiness and can promote wellbeing

What is a hormonal stimulus?

One hormone stimulates the secretion of another

What is a humoral stimulus?

Changes in ion or nutrient blood levels

What is a neural stimulus?

Signals from the nervous system

Steroid hormone

• Are made from cholesterol

• Are lipid-soluble and can easily diffuse across the plasma membrane

• Bind to receptors inside a cell

Amino acid-based hormones

• Vary in size, can be single amino acids, peptides or proteins

• Are lipid insoluble and cannot easily diffuse across the plasma membrane

• Bind to receptors embedded in the plasma membrane

Hypothalamus Posterior Pituitary

1. The cell bodies of neurons within the hypothalamus produce the hormones oxytocin and antidiuretic hormone (ADH).

2. The axons of these neurons form the hypothalamic-hypophyseal tract, which transports these hormones through the infundibulum to the posterior pituitary, where they are stored in the axon terminals.

3. When these hypothalamic neurons are stimulated the stored hormones are secreted from the posterior pituitary into the bloodstream.

Antidiuretic (ADH)

• Stimulus for secretion

• Target organ

• Main action

• When blood Na+ levels increase above the normal range or blood volume and blood pressure decrease below the normal range

• Kidneys

• ADH decreases urine output by stimulating the kidneys to return more water to the blood

  *Can cause the vasoconstriction of arterioles which helps increase blood pressure

• Increases reabsorption of water from the urine being produced and returns it to the blood stream:

  • Dilutes the blood plasma, restoring Na+ levels

  • Restores blood volume and pressure to normal levels

  • Maintains normal blood volume and pressue

Oxytocin

• Stimulus for secretion

• Target organ

• Main action

• Stretching of the uterus during labour

• Uterus

• Stimulates smooth muscle contractions during labour

• Suckling action of the infant during breastfeeding

• Mammary glands

• Stimulates ejection of milk during breastfeeding

Hypothalamus-Anterior Pituitary

1. When stimulated, hypothalamic neurons secrete releasing/inhibiting hormones into the hypophyseal portal system.

2. Hormones travel through the infundibulum via the hypophyseal portal system to the anterior pituitary.

3. Releasing/inhibiting hormones stimulate/inhibit the secretion of anterior pituitary hormones into the bloodstream.

Thyrotropin-releasing hormone (TRH)

• Stimulus for secretion

• Main action

Corticotropin-releasing hormone (CRH)

• Stimulus for secretion

• Main action

Growth hormone-releasing hormone (GHRH)

• Stimulus for secretion

• Main action

Growth hormone-inhibiting hormone (GHIH or somatostatin)

• Stimulus for secretion

• Main action

Gonadotropin-releasing hormone (GnRH)

• Stimulus for secretion

• Main action

Prolactin-inhibiting hormone (PIH)

• Stimulus for secretion

• Target organ

• Main action

• Decreased PIH secretion leads to an increase in PRL secretion

• Mammary glands

• Stimulates milk production

Thyroid Glands

Lies at the base of the throat and it is composed of thyroid follicles which produce and secrete T3 and T4 (a.k.a. Thyroid hormones), and parafollicular cells which produce and secrete the hormone calcitonin.

Parathyroid Gland

Are tiny masses of glandular tissue that produce and secrete parathyroid hormone (PTH). These glands are located on the posterior surface of the thyroid gland.

Thyroid hormone (TH)

• Stimulus for secretion

• Target organs

• Main action

• Thyroid-stimulating hormone (TSH)

• Every cell in the body

Main actions

• Increases basal metabolic rate (BMR), amount of energy required by body cells to carry out all metabolic reactions at rest

• Increases body heat production to maintain a normal body temperature

• Increases HR and force of contraction by increasing the number of B-adrenergic receptors on cardiac muscle cells, regulates normal heart functioning

• Promotes growth of muscles and bones

• Promotes nervous system development

Calcitonin

• Stimulus for secretion

• Target organ

• Main action

• Blood Ca2+ levels increase above the normal range

• Bone

Main actions

• Decreases blood Ca2+ to normal levels by:

  • Inhibiting activity of osteoclasts, specialised bone cells that resorb/digest the extracellular matrix component to release stored calcium into the blood  

  • Stimulating calcium uptake from the blood into bone

Parathyroid hormone (PTH)

• Stimulus for secretion

• Target organs

• Main action

• Blood Ca2+ levels decrease below the normal range

• Bone, kidneys and small intestines

Main actions

• Increases Ca2+ to normal levels by stimulating:

  • Bone-resorbing osteoclasts and the release of stored Ca2+ into the blood

  • Kidneys return more Ca2+ to the blood

• Kidneys secrete calcitriol (the active form of vitamin D) which increases the absorption of Ca2+ from digested food in the small intestines

Erythropoietin (EPO)

• Stimulus for secretion

• Target organ

• Main action

• EPO is secreted by the kidneys when blood oxygen levels drop below their normal range (this is known as hypoxemia).

• EPO targets the bone marrow

• Stimulates the production of red blood cells.

The adrenal glands

The outer adrenal cortex is responsible for the production and secretion of glucocorticoids (primarily cortisol) and mineralocorticoids (primarily aldosterone). The inner adrenal medulla produces and secretes the hormones adrenaline and noradrenaline

Cortisol

• Stimulus for secretion

• Target organs

• Main action

• Anterior pituitary hormone (ACTH)

• Skeletal muscle, liver and adipose tissue

Main actions

• Helps the body resist stressors by increasing blood glucose, fatty acids and amino acid levels by stimulating:

  • Skeletal muscle to breakdown muscle proteins into amino acids

  • Liver to produce glucose from amino acids and glycerol

  • Adipose tissue to breakdown stored fat into fatty acids

• This allows for the production of ATP to resist stressors, from using glucose, fatty acids and amino acids

• Also suppress functions of the immune system by depressing inflammatory and immune responses

Aldosterone

• Stimulus for secretion

• Target organ

• Main action

• An increase in blood K+ levels rise above the normal range

• Kidneys

Main actions

• Maintains blood K+ and Na+ levels by stimulating the kidneys to:

  • §  Remove more K+ from the blood, increases secretion of K+ from the blood into the urine being formed

  • Return more Na+ to the blood, increases reabsorption of Na+ from the urine being formed into the blood

• Restoring and maintaining normal blood volume and blood pressure

Adrenaline and Noradrenaline

• Stimulus for secretion

• Target organs

• Main action

• When the sympathetic nervous system is activated

• Heart, bronchioles, blood vessels, pupils, sweat glands

• Prolong the fight-or-flight response by binding to the alpha or beta adrenergic receptors on the target cells/tissues

The pancreas

b (beta) cells produce and secrete the hormone insulin

a (alpha) cells produce and secrete the hormone glucagon

Insulin

• Stimulus for secretion

• Target organs

• Main action

• Blood glucose levels increase above the normal range (4-8mmol/L)

• Body cells, liver and skeletal muscle

Decreases blood glucose by:

• Stimulating body cells to uptake glucose from the blood

• Targets liver to inhibit the production of glucose from amino acids and glycerol (gluconeogenesis)

• Targets liver and skeletal muscle to inhibit the breakdown of glycogen and glucose (glycogenolysis)

Glucagon

• Stimulus for secretion

• Target organ

• Main action

• Blood glucose levels decrease below normal range

• Liver

Stimulates the liver to:

• Breakdown of stored glycogen to glucose (glycogenolysis)

• Produce glucose from amino acids and glycerol (gluconeogenesis)

• Release glucose into the bloodstream

Ovaries

Produce and secrete oestrogen and progesterone

Testes

Produce and secrete testosterone

Oestrogen

• Stimulus for secretion

• Target organs

• Main action

• FHS and LH

• Female reproductive organs, bones and adipose tissue

Main actions

• Promote growth and maturation

• Targets uterus to regulate the
  menstrual cycle

• Promotes the development of female secondary sec characteristics

• Promotes growth and enlargement of breasts

• Promote growth and feminisation of the skeleton

• Adipose tissue to increase fat storage

Progesterone

• Stimulus for secretion

• Target organs

• Main action

• LH stimulates the ovaries to produce this hormone

• Ovaries

Main actions

• Prepares the uterus for pregnancy and helps maintain the pregnancy

• Helps regulate the menstrual cycle with oestrogen

Testosterone

• Stimulus for secretion

• Target organs

• Main action

• LH stimulates the testes to produce and secrete this hormone

• Male reproductive organs, muscles, bone and hair follicles

Main actions

• Promotes their growth and maturation and targets the testes to stimulate sperm production (spermatogenesis)

• ]Also promotes the development of male secondary sex characteristics

• Increase muscle mass and strength

• Stimulate growth

• Stimulate the growth of body hair

Olfactory pathway

• Chemoreceptors that are bathed in mucus capture and dissolve the odorant

• Olfactory sensory neurons form the olfactory nerve or cranial nerve one where the action potentials travel to the olfactory cortex of the temporal lobe where we are made consciously aware of different odours

• The information then travels to two different places:

  1. Frontal lobe for the smell to be consciously interpreted and identified

  2. Hypothalamus and other regions of the limbic or the emotional system for us to elicit an emotional response to an odour

Gustation pathway

• Gustatory epithelial cells found in taste buds, microvilli are bathed in saliva on the surface of the tongue which is where food chemicals are dissolved

• Impulses travel from the taste receptors up to the medulla via the facial nerve, glossopharyngeal and the vagus nerve where they will then travel to the gustatory cortex of the insula

• Fibres then travel on the hypothalamus in the limbic system so that you can get an emotional response and an appreciation to taste is elicited

Pinna - Function

Funnels sound into external acoustic meatus

External acoustic meatus - Function

Allows sound waves to travel down and vibrate the tympanic membrane

Tympanic membrane - Function

Vibrates in response to sound waves and it then transfers this sound energy as waves into mechanical energy in bones

Auditory ossicles - Function

Includes the malleus, incus and stapes which transmit and amplifies the vibratory motion of the tympanic membrane through the middle ear to the oval window

Oval window - Function

Window in the wall of the cochlea. On one side has the stapes embedded in the window and the other side the perilymph. Movement causes pressure within the perilymph

Round window - Function

Absorbs pressure waves to wait for a new sound to come through

Cochlear - Function

Spiral shaped structure that contains the cochlear duct