Nervous system, endocrine system, Homeostatis Flashcards
Systems contributing to coordination
nervous system and the endocrine system.
Fore brain consists of
Cerebrum, thalamus, hypothalamus and pineal body
Hind brain consists of
Cerebellum, pons varolli and medulla oblongata
Cerebro-ventricles
Central canal of the brain forms 4 irregular shaped cavities called ventricles. Three ventricles are present in the forebrain and 1 in the hind brain.
Central canal and ventricles are filled with cerebro-spinal fluid.
Functions of cerebrospinal-spinal fluid
Maintains uniform pressure within the CNS.
Acts as a shock absorber between brain and the skull
Circulates nutrients, hormones as well as to remove waste matter.
Protection of CNS
Brain is enclosed by a skull while the spinal cord is surrounded by the vertebral column.
Further protection is given by 3 meninges known as dura matter (outermost), Pia matter (innermost) and in between the arachnoid matter.
Thalamus
Located in the cerebral hemisphere just below the corpus callosum.
Acts as the main input centre for sensory information from special sense organs and sensory receptors in the skin and integral organs. These sensory information are sent to specific locations in the cerebral cortex for further processing.
It mainly relays and redistribute nerve impulses from most parts of the brain to the cerebral cortex.
Hypothalamus
Located below and infront of the thalamus immediately above the pituitary gland.
Connected to the posterior lobe of the pituitary gland by nerve fibres and to the anterior lobe of the pituitary gland by a complex system of blood vessels.
Regulates body temperature Regulates thirst and water balance Regulates appetite Regulates sleep and wake cycles Control of autonomic nervous system Initiates fight or flight response Plays a role in sexual behaviour Source for posterior pituitary hormones and releasing hormones that acts on anterior pituitary
Mid brain
Mid brain is the upper part of the brain stem. Situated between the cerebrum above and pons varolli below surrounding the crebro-spinal fluid filled connections of the 3rd and the 4th ventricles.
Acts as a relay station for ascending and descending nerve fibres
Receives and integrates sensory information (auditory and visual) and sends it to particular regions of the forebrain
Coordinates auditory and visual reflexes
Pons varoli
Situated infront of the cerebellum below the midbrain and above the medulla oblongata
Transfer information between the PNS and the forebrain and midbrain
Coordinates large scale body movements climbing and running
Together with the medulla oblongata helps regulate respiration
Medulla Oblongata
Lowest part of the brain stem situated below the pons varolli and is continuous with the spinal cord. Consists of respiratory center, cardiovascular center and reflex centres.
Transfer information between the PNS and the forebrain and midbrain.
Coordinates large scale body movements such as running and climbing.
Controls several autonomic, homeostatic functions including breathing, heart and blood vessel activities.
Controls involuntary reflexes such as vomiting, swallowing, coughing, sneezing through reflex centres.
Cerebellum
Located behind the pons varoli and below the posterior part of the cerebrum
Coordinates voluntary muscle movements
Maintains posture and balance
Helps in learning and remembering motor skills
Spinal cord
I the spinal cord outer region is composed of white matter while the inner region is composed of grey matter
Links the CNS to sensory neurones and motor neurones and facilitates nerve impulse propagation towards the brain and away from the brain.
Coordinates and produces reflexes
Antagonistic
Opposite
2 divisions of autonomic nervous system
Sympathetic stimulations prepare the body to deal with exciting/stressful and energy generating situations (fight of flight)
Parasympathetic division causes opposite responses that promote calming or return to self-maintenance functions (rest and digest)
Parasympathetic nerves exit the CNS at the base of the brain and spinal cord as cranial nerves or spinal nerves respectively. On the other hand sympathetic nerves exit only from the spinal cord.
Constricts pupil of the eye
Parasympathetic
Inhibits salivary gland secretion
Sympathetic
Constricts bronchi in lungs
Parasympathetic
Accelerates heart
Sympathetic
Stimulates activity of the stomach and intestine
Parasympathetic
Inhibits activity of the pancreas
Sympathetic
Stimulates gall bladder
Parasympathetic
Stimulates adrenal medulla
Sympathetic
Promotes emptying of bladder
Parasympathetic
Promotes ejaculation and vaginal contractions
Sympathetic
Resting potential
When a neurone is at rest (not sending a signal/non conducting) the membrane potential is called the resting membrane potential. -60 mV to -80mV
Maintained by the distribution ion concentrations inside and outside of the cell
Concentration of K+ is higher inside the cell while the concentration of Na+ is higher outside the cell. In addition Cl- and large proteins anions are present inside the cell. Due to this there is a relative negative charge inside the cell and a positive charge outside the cell.
Selective permeability of the membrane to K+ and Na+ ions
There are more potassium channels open than sodium channels. As a result there is a net negative charge inside the cell.
Sodium-pottasium pump
This pump transports 3 Na+ out of the cell for every 2 K+ that is transports in. This pump uses ATP to actively transport these ions.
Action potential
An action potential occurs due to the change in the membrane potential above a threshold level due to a stimulus. Consists of depolarization, repolarization and hyperpolarization.
Depolarization
A change in the membrane potential such that inside of the cell is made less negative relative to the outside. Depolarization results due to Na+ inflow in response to a stimulus.
Repolarization
Sodium channels close blocking the inflow of Na+. However most potassium channels open permitting K+ outflow making inside of the cell negative.
Hyperpolarization
Sodium channels are closed but potassium channels are opened. As a result inside of the cell becomes more negative.
Refractory period
Short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of sodium channels. This prevents reverse conduction of an impulse in an axon.
Conduction of a nerve impulse
A series of action potentials that move along an axon is known as a nerve impulse
Axon potential spreads to the neighbouring location while the initial location repolarizes
The speed of conduction depends on
Conduction speed increases with the diameter of the axon
Precense of myelinated axon
Synapses
A synapse is a junction where a neurone (presynaptic cell) communicates with a postsynaptic cell across a narrow gap (synaptic cleft).
Neurotransmitter
Neurotransmitters are molecules secreted at synaptic terminals of presynaptic neuron, diffused across synaptic cleft, bind to receptors at the postsynaptic membrane, triggering a response.
Common neurotransmitters
Acetylcholine Some amino acids Biogenic amines Neuropeptides Some gases
Schizophrenia
This is a severe mental disturbance characterized by psychotic episodes in which patients have distorted perception of reality. Evidence suggests that this affects neural pathways that use dopamine as a neurotransmitter.
Alzheimer’s disease
This is a severe mental deterioration (dementia) characterized by confusion and memory loss. Cause of this is due to the progressive and irreversible degeneration of neurones in the brain especially in the cerebral cortex.
Parkinson’s disease
This is a progressive motor disorder that leads to lack of control and coordination of muscle movements. Associated with the gradual degeneration of dopamine neurotransmitter releasing neurones in the brain.
Infoldings present in the cerebral cortex increasing surface area
Gyri and Sulci
Diffused and localised
E.g: While localized TGCT is a clearly defined tumor, diffuse TGCT is spread out so that “you can’t draw a circle around it,” says Bernthal. “With the localized type, you can see where it begins and where it ends, whereas with the diffuse type, it looks like the roots of a tree
Portal blood vessels
They starts and terminates with blood capillary beds
Tropic hormones
Hormones of which the target site is another endocrine gland
Only part in the nephron where water reabsorption does not occur
Ascending limb of the loop of henle
Gluconeogenesis
Gluconeogenesis is a process that transforms non-carbohydrate substrates (such as lactate, amino acids, and glycerol) into glucose
What is the gland and the hormone that it secretes which increases immunity
Thymosin secreted by the thymus
Structure secreting cerbro spinal fluid
Lining epithelium of cerebro ventricles
Structural differences of sympathetic and parasympathetic nerves
Parasympathetic nerves contains both cranial nerves and spinal nerves originated from the brain and the spinal cord respectively while sympathetic nerves contains only spinal nerves.
Sympathetic pre-ganglionic neurones are shorter and post-ganglionic neurones are longer.
Parasympathetic pre-ganglionic neurones are longer and post-ganglionic neurones are shorter
Hormones released from the hypothalamus
7 hormones are acting on the anterior pituitary (5 releasing hormones and 2 release inhibiting hormones)
Other 2 hormones oxytocin and antidiuretic hormones are produced by the hypothalamus and stored in the posterior pituitary.
GHRH
Growth hormone releasing hormone
Stimulates the secretion of growth hormone (GH) from anterior pituitary
TRH
Thyrotropin releasing hormone
Stimulates the secretion of thyroid stimulating hormone (TSH) from anterior pituitary
CRH
Corticotropin releasing hormone (CRH)
Stimulates the secretion of adrenocorticotropic
hormone (ACTH) from anterior pituitary
GnRH
Gonadotropin releasing hormone
Stimulates the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from anterior pituitary
PRH
Prolactin releasing hormone
Stimulates the secretion of prolactin hormone from
anterior pituitary
PIH
Prolactin inhibiting hormone
Inhibits the secretion of prolactin hormone from
anterior pituitary
GHRIH
Growth hormone release inhibiting hormone
Inhibits the secretion of GH and TSH from the
anterior pituitary
Growth hormone shows
Both tropic and non-tropic properties
Most abundant hormone secreted by the anterior pituitary
GH
GH
All body cells
Promotes tissue growth (especially bones and muscles) by stimulating protein synthesis; Regulates metabolism
TSH
Thyroid gland
Stimulates secretion of thyroid hormones (triiodothyronine and thyroxin); Stimulates growth of thyroid gland,
ACTH
Adrenal cortex
Stimulates secretion of adrenal cortex hormones (Glucocorticoid hormones)
FSH
Ovary - Stimulates growth and development of ovarian follicle
Testis - Stimulate spermatogenesis
LH
Ovary- Ovulation; promote formation
of corpus luteum in the ovary (structure formed after ovulation) and stimulates progesterone hormone secretion by the corpus luteum.
Testes - Stimulates secretion of testosterone hormone
Prolactin
Mammary gland
Stimulates milk production; Together with other hormones (oxytocin) promotes milk secretion by the mammary glands.
Difference between anterior and posterior pituitary glands
Posterior pituitary gland does not synthesises hormones
ADH
Vasopressin, also called antidiuretic hormone
Distal convoluted tubules of the nephrons and collecting ducts in the kidney
Stimulates resorption of water by increasing permeability to water
Oxytocin
Mammary gland-Stimulates milk ejection by stimulating contraction of smooth muscles
Uterine muscles-Promotes parturition by contraction of smooth muscles
Thyroid gland
Located in the neck in-front of the trachea. Releases triiodothyronine (T3) and thyroxin (T4). Increases the basal metabolic rate.
Calcitonin helps to lower blood calcium ion level if it raised above the normal limit. Promotes storage of Ca2+ ions within bones and inhibits reabsorption of Ca2+ in kidney tubules.
Parathyroid glands
Set of 4 small glands embedded in the posterior surface of the thyroid gland.
Secretes parathyroid hormone (PTH). Main function of PTH is to promote high Ca levels by stimulating Ca2+ reabsorption, absorption through the small intestine and promotes release of Ca from bones by acting on bone destroying cells.
Thymus gland
Thymus gland is located in the upper part of the chest, directly behind the sternum and between the lungs. Thymus gland secretes the hormone thymosin. Thymosin acts on the lymphocytes and regulates development and maturation of T lymphocytes.
Pineal glands
Melatonin secreted by the pineal gland is involved in the regulation of biological rhythms related to reproduction and daily activity levels. Associated with coordination of circadian and diurnal rhythms of many tissues and inhibition of growth and development of sex organs before puberty.
Adrenal glands
two parts: adrenal cortex (outer) and adrenal medulla (inner). Hormones secreted can mediate stress responses.
Hormones mainly produced by the adrenal cortex and their functions
Glucocorticoids and mineralocorticoids.
Glucocorticoids have a main effect on glucose metabolism and promote glucose synthesis from non-carbohydrate sources such as protein and fat.
Main mineralocorticoid produced by the adrenal gland is aldosterone which is involved in maintaining water and electrolyte balance
Adrenal cortex hormones are steroids
Main glucocorticoid produced by the adrenal gland
Cortisol
Main mineralocorticoid produced by the adrenal gland
Aldesterone
Hormones mainly produced by the adrenal medulla and their functions
Adrenaline (epinephrine) and noradrenaline (norepinephrine) which could mediate ‘short term stress responses which can potentiate the “fight or flight response” by increasing the heart rate and blood pressure, diverting blood to essential organs (i.e heart, brain, skeletal muscles) and increasing metabolic rate etc
Islets of Langerhans in the pancreas
The endocrine part of the pancreas is the islets of Langerhans. Liver and skeletal muscles are the main target sites of these hormones
Gonads
Paired female gonads (ovaries) are located in the pelvic cavity. Paired male gonads (testes) lie in the scrotum.
Ovarian follicle produces the hormone estrogen.
In addition ovaries and testes secrete inhibin that inhibits secretion of FSH from anterior pituitary.
Regulatory systems operating with positive feedback mechanisms
Positive feedback mechanisms involving oxytocin hormone operate in childbirth and breast milk ejection.
Type 2 diabetes mellitus
Known as non-insulin dependant diabetes mellitus.
Even though insulin is produced and secreted into the blood, target cells fail to take up glucose from the blood.
Hyperthyroidism
occurs due to exposure of body tissues to excessive levels of T3 and T4. Common effects include increased basal metabolic rate, weight loss, warm, sweaty skin and diarrhea. Some conditions lead to bulging of eyes
Treatment may include surgical removal of part or all of the thyroid gland and using medicine to block thyroid hormone synthesis.
Hypothyroidism
Insufficient secretion of thyroid hormones (T3 and T4) can be due to lack of TSH production by anterior pituitary or iodine deficiency in diet. Common effects include low basal metabolic rate, weight gain, lethargy, dry, cold skin and constipation.
Normal body temperature of man is typically
37’C (36.50’C – 37.50’C)
Heat loss mechanisms
- dilation of blood vessels in the skin which causes filling of blood capillaries with warm blood and radiating heat from the skin surface
- increase sweat secretion from the sweat glands which promotes heat dissipation through
evaporative cooling
Heat gain mechanisms
- constriction of blood vessels in the skin which divert the blood from the skin to deeper tissues thereby reducing heat loss through the skin surface
- shivering: rapid repetitive contractions of skeletal muscles to generate heat
- contracting hair erector
muscles to generate heat to some extent - stimulating secretions of more thyroid hormones (e.g. thyroxin) and adrenalin into the blood which increase the metabolic rate and cellular metabolism (especially oxidation of fat in the liver) to produce more heat
Normal bood glucose level
70 – 110 mg/100 mL (while fasting)
Homeostatic blood osmolarity level
300 mOsmol/l
Role of liver in homeostasis
Carbohydrates, protein and fat metabolism
Breakdown of erythrocytes and defence against microbial infections
Detoxification of drugs and toxicants
Production of heat
Storage of nutrients
Inactivation of hormones
Secretion of bile
3 neurones in the reflex arc
Afferent (sensory)
Efferent (motor)
Inter
Blance receptors are found in the
Ampullae of semi-circular canals and in the vestibules (utricle and saccule)
Shunt vessels
A blood vessel that links an artery directly to a vein
