Physiology 101 test 1

What are the two parts of the adrenal glands?

• Superficial adrenal cortex

• Inner adrenal medulla

What type of gland is an adrenal gland

endocrine

what is the sections the adrenal cortex is divided into

zona glomerulosa

zona fasciculata

zona reticularis

what hormones is found in the adrenal cortex

corticosteroids/ adrenocorticol steriods

what type of steroids is found in the zona glomerulosa? and what is its function

Mineralocorticoids

Affect the electrolyte composition of body fluids

• Regulate electrolyte concentration of the ECF, especially Na and K+

Targets: Aldosterone - in kidneys

what type of steroids is found in the zona fasciculata? and what is its function

Glucocorticoids

• Maintain blood sugar levels and movement of water into and out of cells

  • Increase rate of glucose synthesis and glycogen formation

• Also anti-flammatory and immunosuppressive

• Secretion controlled by negative feedback

• Stress induces increased secretion of cortisol

what type of steroids is found in the zona reticularis? and what is its function

Androgens

• Released in response to ACTH

• Sexual differentiation in puberty

what hormones does the adrenal medulla produce?

• Epinephrine (adrenaline)

• Norepinephrine (noradrenaline)

what are the functions of the hormones in the adrenal medulla?

• Under direct control of the sympathetic nervous system

• During flight/flight response the sympathetic nerve stimulates the

adrenal medulla to release E (80%) and NE (20%)

• Cortisol from the adrenal cortex is necessary to covert NE into E

• Actions:

  • Increase glycogen mobilisation in skeletal muscles to increase ATP

  • Increase release stored fats for energy

  • Increase cardiac output

  • Increase blood glucose by breakdown of liver glycogen stores

what kind of gland is the pancreas?

BOTH endocrine and exocrine glands

what are the 4 pancreatic islet cell hormones?

• alpha cells

• beta cells

• delta cells

• F cells

what does the alpha cell secrete? and function?

• secrete glucagon

• Raises blood glucose

what does the beta cell secrete? and function?

• secrete insulin

• Lowers blood glucose

what does the delta cell secrete? and function?

• secrete somatostatin

• Inhibit glucagon and insulin secretion

• Slows nutrient absorption from GI tract

what does the F cell secrete? and function?

• secrete pancreatic polypeptide

• Inhibits gallbladder contraction

• Regulates secretion of pancreatic digestive enzymes

• Inhibited by somatostatin secretion

what happens when blood glucose levels rise?

Beta cells secrete insulin, stimulates transport of glucose across cell membranes (into cells)

what happens when blood glucose levels drops?

Alpha cells secrete glucagon, stimulates glycogen breakdown and glucose release by liver

what is the function of insulin?

• Circulating insulin lowers blood sugar by increasing membrane transport of glucose into:

  • Muscle

  • Connective tissue

  • WBCs

• Once glucose enters the cells, insulin binding triggers enzymatic activities

  • Catalyses oxidation of glucose for ATP production

  • Joins glucose molecules together to form glycogen

  • Converts glucose to fat

• As cells take up glucose, plasma levels drop and insulin secretion is suppressed

what are the effects of insulin?

1. Accelerates glucose uptake

2. Accelerates glucose utilisation and enhanced ATP production

3. Stimulates glycogen formation

4. Stimulates amino acid absorption and protein synthesis

5. Stimulates triglyceride formation in adipose tissue

what are the effects of glucagon?

• Secretion of glucagon is stimulated by low blood sugar levels and also high levels of amino acids in the blood

1. Stimulates breakdown of glycogen in skeletal muscle and liver cells (glycogenolysis)

2. Stimulates breakdown of triglycerides in adipose tissue

3. Stimulates production of glucose in liver (gluconeogenesis) (Liver cells absorbs amino acids from blood and convert them to glucose)

what are the signs of diabetes?

1. Polyuria

• Large urine output

• Excess glucose prevents water reabsorption in the nephron

• Decrease in blood volume and dehydration

 

2. Polydipsia

• Excessive thirst from dehydration

 

3. Polyphagia

• Excessive hunger and food consumption

what are the types of diabetes

• Type I insulin-dependent diabetes

  • Autoimmune destruction of beta cells in pancreas

  • Requires insulin

 

• Type II non-insulin dependent diabetes

  • Begins as insulin resistant in tissues, due to defective glucose receptors and signalling mechanisms

  • Adult onset >40 years

  • Heredity disposition

  • Overweight/bad diet

  • Can usually be treated by diet and exercise

what are the functions of the skin?

1. Protects underlying tissues and organs

2. Excretes salts, water, and organic wastes (glands)

3. Maintains body temperature (insulation and evaporation)

4. Synthesises vitamin D3

5. Stores lipid

6. Detects touch, pressure, pain and temperature

what is the structure of the skin

Epidermis

• Outer, thinner layer

• Composed of epithelium

 

Dermis

• Inner, thicker layer

• Composed of connective tissue

• Nerves

 

Hypodermis (subcutaneous) layer

• Fat store

• Blood vessels

what is the structure of the epidermis?

1. Stratum corneum

• Multiple layers of dead, flat keratinocytes which are continuously shed and replaced by cells from deeper strata

• Water resistant but not waterproof

2. Stratum lucidum

• Dead keratinocytes

• Present in thick skin which is subjected to increased friction

 

3. Stratum granulosum

• Keratinocytes produce keratin and keratohyalin and cells start to die

• Lamellar granules secrete waterproofing chemical

 

4. Strata spinosum

• Desmosomes hold cells together

5. Stratum basale or stratum germinativum

• Attached to a basement membrane

• Made of stem cells (basal cells) which continuously divide, melanocytes, dendritic cells (Langerhans cell) and tactile cells (merkel cells)

what are the 4 types of cells within the skin

1. Keratinocytes

• Produce keratin

• Waterproofing sealant

2. Melanocytes

• Produce melanin

3. Langerhans cells

• Unique population of macrophages

• Involved in the immune response

4. Merkel cells

• Detect touch

what is the dermis made out of?

papillary layer

reticular layer

what is the papillary layer made out of?

• Superficial layer made of areolar tissue

• Small capillaries, lymphatics, sensory neurons

• Sensory receptors: tactile corpuscles (light touch)

what is the reticular layer made out of?

• Deeper layer made of dense irregular connective tissue

• Collagen and elastic fibres provide strength and flexibility

• Larger blood vessels, lymph vessels and nerve fibres (eg sensory receptors and neurons)

what is the function of the hypodermis layer?

• Connects the dermis to underlying tissue

• Made of loose connective tissue with fat cells

• Contains large blood vessels with no vital organs

what is the function of nerves in the dermis?

• control blood flow

• Regulate gland secretions

• Sensory receptors detect sensation

what contributes to epidermal pigmentation

• Pigments Carotene and Melanin

• Circulation of Blood (red blood cells)

what is carotene?

• Orange - yellow pigment

• Accumulates with epidermal cells and fatty tissues of the dermis

• Can be converted to vitamin A (retinal)

what is melanin?

• Yellow-black pigment which is dependent on the enzyme called tyrosinase for its production

• Produced by cells called melanocytes in the stratum basale of the epithelium

• Stored and transported within melanosomes to keratinocytes

• Protects DNA in our skin cells from sun damage

what is hair?

• Hairs are non living structures produced in hair follicles

• Hair is composed of columns of dead, keratinised cells held together by extracellular proteins

  • Shaft: superficial portion

  • Root: anchors the hair to the skin

what does hair do?

• Protects and insulates the skull

• Guards openings against particles and insects

• Is sensitive to very light touch

Why does hair vary in colour?

• Hair colour results from the amount and type of melanin in keratinised cells

• Grey hair is due to the progressive decline in the synthesis of tyrosinase enzyme

what are the types of glands?

• Sebaceous (oil glands)

• Apocrine sweat glands

• Merocrine (eccrine) sweat glands

• Ceruminous glands

• Mammary glands

what is a Sebaceous (oil glands)

• Majority of glands are connected to hair follicles and discharge an oily lipid secretion called sebum into the follicle

• Sebum is bade of triglycerides, cholesterol, proteins and ions which inhibits bacterial growth, conditions the skin and protects the hair shaft

what is an apocrine sweat gland?

• Limited in distribution to the skin of the axilla (arm pit), areolae (around nipples), pubis (groin) and beard are in males

• Ducts into hair follicles

• Sticky, cloud secretions which sometimes produce an odor

• Do not begin to function until puberty

what is a Merocrine (eccrine) sweat glands

• Widely distributed on the body surface, especially the palms of hands and soles of feet

• Fluid is directly secreted onto the surface of the skin through a pore

• Fluid is made of water and ions

• Main functions is in the regulation of body temperature ie heat loss

what is a Ceruminous glands

• Modified sudoriferous glands

• Located in external auditory canal

• Produce waxy substance called cerumen (ear wax)

  • Impedes entrance of foreign bodies

what is a mammary gland

Specialised sweat glands

what are nails?

• Plates of tightly packed, hard, keratinised epidermal cells

• Protect the exposed surfaces of the finger and toe tips

• Consist of a nail body and nail root from where the nail grows

what are the parts of the nails?

1. Lunula

• Area of thickened stratum basale

 

2. Hyponychium (nail bed)

• Area of thickened stratum corneum

• Secures nail to tip of digit

 

3. Eponychium (cuticle)

• Narrow band of epithelium occupying proximal border of nail

what happens during Epidermal wound healing

• Basal cells of epidermis break contact with basement membrane

• Enlarge and migrate across wound - stimulated by EGF

• Stop migration due to contact inhibition

• Relocated cells divide to build new epidermal layers and thicken epidermis

what happens during Deep wound healing

1. Inflammatory phase

• Blood clot forms, loosely binding wound edges

• Inflammation

 

2. Migratory phase

• Clot becomes a scab

• Epithelial cells migrate beneath scab to bridge wound

• Fibroblast migrate and form collagen

 

3. Proliferative phase

• Extensive growth of epithelial cells beneath scab

• Random deposition of collagen fibres

• Blood vessel growth

 

4. Maturation phase

• Collagen fibres become organised

• Epithelium restored to normal thickness and scab sloughs off

• Blood vessels restored

what is damaged during UVA exposure

• Skin tanning (trigger melanin production)

• Long term damage

what is damaged during UVB exposure

• Main cause of sunburn

• DNA damage in epidermal cells

what are the effects of ageing on the skin?

• increased skin injuries and infections

• Immune system is reduced

• Muscles become weaker

• Decreased in bone strength

• Increased sensitivity to the sun

• Skin dries and becomes scaly

• Hair changes

• Reduced ability to lose heat skin repair slows

what is thermoregulation?

• The integumentary and sympathetic nervous system work together to maintain body temperature

• The nervous system continuously monitors body temperature and initiates a response when the temperature becomes too high or too low

• Response include:

  • Changing the diameter of skin blood vessels

  • Perspiration

how does the body regulate cutaneous blood flow

• As the bodies core temperature increases, blood vessels in the dermis dilate causing heat in the blood to be lost through the skin by radiation and convection

• When our body temperature drops the blood vessels in our dermis constrict reducing blood circulation

• Our skin will feel cool, but heat loss will be reduced and viscera will remain warm

• Frostbite can occur when our skin 'freezes' when trying to maintain our core temperature

explain the types of perspiration and the differences?

• Insensible perspiration

  • Interstitial fluid lost by evaporation through the stratum corneum

  • Even when not visibly sweating up to 500 mL of fluid can be lost each day

• Sensible perspiration

  • Activation of sweat glands to secrete sweat (99% water and electrolytes including sodium chloride)

  • Evaporation of sweat from the skin surface cools the body

what is in the CNS

brain

spinal chord

what is the function of the CNS

PROCESS and CO-ORDINATE:

• Sensory data

• Motor commands

• Higher functions of the brain

what is in the PNS

spinal nerves

cranial nerves

what is the function of the PNS

TRANSMIT INFORMATION

• Carries sensory information from the body to the CNS

• Carries commands from CNS to the body

what is the structure of the spinal chord

• Nervous tissue found within protective membranes (meninges) and a bony vertebral column

• Central canal filled with cerebrospinal fluid (CSF)

• Divided into 32 segments based on the spinal region and origin of the spinal nerve

  • Each segment has a pair of dorsal root ganglia (DRG) close to the spine, dorsal roots and ventral roots

  • Each segment has a region of 'gray matter' and a region of 'white matter'

what is the function of the spinal chord

• Transmission of sensory information to the brain

• Transmission of motor commands from the brain

• Integration of information

• Autonomic control of spinal reflexes

what is gray matter and what is the function?

• Shaped like a letter H or butterfly and called horns

• Integrates information and initiates commands from the PNS

  • Nuclei

  • Neuroglia

  • Unmyelinated axons

what is white matter and what is the function?

• Carries information into and out of the CNS along nerve tracts

  • Ascending tracts carry information to the brain

  • Descending tracts carry information away from the brain

what is the spinal nerves and what is the function?

• Spinal nerves extend into the periphery forming the peripheral nerves that innervate body tissues and organs

• Spinal nerves contain both sensory neurons and motor neurons and therefore are called mixed nerves

• Each spinal nerve is surrounded by connective tissue

  • Epineurium - outer layer

  • Perineurium - middle layer

  • Endoneurium - inner layer

what is a dermatome?

• Bilateral region of skin surface monitored by a single pair of spinal nerves

• Clinically, damaged to a spinal nerve or ganglia results in loss of sensation in the corresponding skin region

what is a spinal reflex

• Rapid, automatic nerve responses triggered by specific stimuli

• Controlled by spinal cord alone, not the brain

• Produce simple and complex reflexes depending on the number of neurons in the circuit

what neurons are involved in the circuit?

Interconnected sensory neurons, motor neurons, and interneurons

explain the steps of a reflex arc

what is the difference between a somatic and visceral reflex?

• Somatic reflexes associated with involuntary control of the muscular system ie stretch reflex (knee jerk reflex)

• Visceral reflexes associated with changes in internal systems and can be referred to as autonomic reflexes

what is a monosynaptic reflex?

• A sensory neuron synapses directly with a motor neuron creating one synapse

• Very fast

• Simple reflexes

what is the stretch reflex?

• Tendon hammer activates the receptor - muscles spindle

• Stretching of the muscle spindle activates the sensory neuron

• Stimulation and activation of the motor neuron

• Rapid contraction of the effector

what is the muscle spindle?

• Sensory receptors involved in the stretch reflex

• Small intrafusal nerve fibres

• Large skeletal muscle fibres called extrafusal fibres which perform the muscle contraction

• The tendon hammer stretches the intrafusal fibres which stimulates the sensory neuron

• The motor neuron is stimulated which then activates the extrafusal fibre producing a reflex response

what is a polysynaptic reflex/

• The response is more complicated than a monosynaptic reflex

• A sensory neuron synapse with a pool of interneurons before synapsing with a motor neuron creating multiple synapses

• More than one muscle group can be activated at the same time

• Interneurons can cause both excitatory post synaptic potentials or inhibitory post synaptic potentials

• Some muscles may be stimulated while other muscles may be inhibited

• Several reflexes may take place to produce a coordinated, controlled response

what is a golgi tendon reflex?

Protects muscles from excessively heavy loads by causing the muscle to relax and drop the load

what is a golgi tendon organ in a sensory receptor?

• Sensory nerve endings interwoven with collagen fibres

• Stimulating the receptor activates sensory neurons which stimulate inhibitory neurons in the spinal chord (1)

• Interneurons synapse with the motor neurons inhibiting their activity (2)

• Therefore the skeletal muscle cannot create enough tenson or force to hold the load (3)

what is the withdrawal reflex?

Moves affected parts of the body away from a stimulus

 

Eg flexor reflex - as one muscle contracts the opposing muscle relaxes

what is a crossed extensor reflex?

Eg when you step on a tack

 

• Flexor reflex and crossed extensor reflex working together at the same time

what are the main brain regions?

• Cerebrum

• Cerebellum

• Diencephalon

  • Thalmus

  • Hypothalamus

  • Pineal gland

  • Pituitary gland

• Brain stem

  • Midbrain

  • Pons

  • Medulla oblongata

• Limbic system

what is in the brain stem?

• Midbrain

• Pons

• Medulla oblongata

what is the medulla oblongata?

• Transmission of information between the spine and brain

• Autonomic nuclei controlling visceral activities

  • Cardiovascular centre

    • Adjusts heart rate, heart contractions, blood flow

  • Respiratory rhythmicity centre

    • Regulates the breathing rate

what is the pons?

 

• Links the cerebellum with the midbrain, diencephalon, cerebrum and spinal chord

• Location of nuclei and tracts that process information sent to or from the cerebellum

• Location of nuclei which controls the activity of the respiratory rhythmicity centres in the medulla oblongata

what is the mid brain?

• Processes and regulates hearing (auditory) and visual information

• Controls alertness

what does the Superior colliculi do?

• Processes visual information

• Controls the reflex movements of eyes, head & neck in response to visual stimuli tracking

what does the Inferior colliculi do?

• Receives hearing information from the medulla oblongata and pons

• Controls the reflex movements of the head, neck and torse in response to auditory stimuli such as loud noise

what is the cerebellum?

• Cauliflower appearance

• Coordinates movements at the subconscious level

• Coordinates information to maintain body balance and equilibrium - monitors proprioceptive information

• Fine tunes learned movements such as walking (gait), riding a bicycle, playing an instrument

what is in the Diencephalon?

thalamus

hypothalamus

what is the funciton of the thalamus?

• Filters ascending sensory information to the cerebral cortex

• Relays information from the cerebellum to the cerebral cortex

• Crude recognition of:

  • Pain

  • Temperature

  • Pressure

what is the funciton of the hypothalamus?

• Major regulator of homeostasis

• Controls autonomic function

• Subconscious control of skeletal muscle

• Coordinates the nervous and endocrine systems

• Regulates body temperature

• Circadian rhythms

• Emotions and behaviour

what is the funciton of the limbic system?

Functional grouping

• Establishes emotional states

• Links conscious functions of cerebral cortex with autonomic functions of brain stem

• Facilitates memory storage and retrieval

what is the funciton of the cerebrum?

• Largest part of the brain

• Controls all conscious thoughts and intellectual functions

• Process somatic sensory and motor information

• Has 4 lobes (occipital - vision, temporal - auditory, frontal - sensory information, parietal -motor information)

1. Each cerebral hemisphere receives sensory information from and sends motor commands to, the opposite side of the body

2. The two hemispheres have different functions, although their structures are alike

3. Correspondence between a specific function and a specific region of cerebral cortex is not precise

what is the function of the cranial nerves?

 

• 12 pairs connected to brain

• 4 classifications

• Sensory nerves - carry somatic sensory information, including touch pressure, vibration, temperature and pain

• Special sensory nerves - carry sensation such as smell, sight, hearing, balance

• Motor nerves - axons of somatic motor neurons

• Mixed nerves - mixture of motor and sensory fibres

what is a receptor?

• Specialised cells that monitor specific conditions in the body or external environment

• Detects a stimulus and converts to an action potential which travels to the CNS via sensory neurons

• Receptors are classified by the type of stimulus that excites them

• Each receptor has a characteristic sensitivity which is called receptor sensitivity eg touch receptor vs taste (chemical) receptor

what are the types of receptors?

• Nociceptor

  • Pain

• Thermoreceptor

  • Temperature

• Chemoreceptors

  • Chemical concentration

• Mechanoreceptor

  • Tactile receptors: touch, pressure, vibration

  • Baroreceptors: organ pressure

  • Proprioceptors: muscle contraction, position of joints

what is a receptive field?

Each receptor detects a stimulus within a specific area

what are the types of receptive fields and what does it mean?

• Small receptive field provide detailed information - fine touch and pressure tactile receptors

• Large receptive field provides less detailed information - crude touch and pressure tactile receptors

what is a two point discrimination test?

• Two point discrimination to test tactile sensitivities is often used in the clinic

  • Provides a detailed map of tactile receptors - when two points are within a receptive field the patient will report only one point of contact

what is a labelled line?

• Detected information follows a specific neuronal pathway to the cortical region of the brain

• One type of receptor responds to one specific modality

• Nerve attached to the receptor can only carry that type of sensation

what is a receptor adaptation

• Changes in receptor sensitivity in the presence of a continual stimulus ie nature of the receptor response to the stimulation

• Peripheral adaptation occurs when the amount of receptor activity changes

what is a tonic receptor?

• Always active and adapt slowly

• Pain receptors

what is a phasic receptor?

• Rapidly adapting and have reduced activity

• Temperature receptors - eg entering a cool room on a hot day

what is a somatosensory pathway?

• Sensory information from the skin, head, neck, limbs and muscle of body wall