organ systems

spinal cord

provides link between the brain and rest of the body. acts as a minor coordinating centre (some simple reflexes)

somatic nervous system

voluntary. effects skeletal muscles. only one efferent neuron. conscious control.

autonomic nervous system

involuntary. effector organs: smooth muscle, cardiac muscle, glands. two efferent neurons and ganglia. non-conscious control.

ganglia

specialised collections of cell bodies

polysynaptic pathway

gives potential to affect more tissues, influence depending on what is released when→ greater control.

how does a synapse work

-sodium comes down axon, depolarising from -70 to 0-30 mV.

-voltage gated calcium channels open→ calc floods in down conc gradient

-3 proteins attach vesicle to membrane, and when calcium sensor detects rise, twists so the vesicle and membrane fuse together.

-vesicle contents released

-at post-synaptic nerve, ach binds to receptor and causes influx of sodium → depolarisation.

how is ach removed from receptor keeping sodium channels open

acetylcholine esterase breaks up ach into acetate and choline.

what is ANS regulated by

hypothalamus. can be neuronal or hormonal

2 types of ANS activity

parasympathetic and sympathetic

parasympathetic activity

non-emergencies. long pre-ganglionic fibre

sympathetic activity

emergencies (fight or flight), short pre ganglionic fibre

ganglion

cluster of nerve cell bodies, acting as a relay point or connection between different parts of the nervous system

two types of acetylcholine receptors

nicotinic receptors, muscarinic receptors

nicotinic receptors

direct and fast, depolarisation, neuromuscular junctions

muscarinic receptors

excitatory:

indirect and slow, depolarisation, synapses in CNS,ANS,PNS

inhibitory:

indirect and slow, hyperpolarisation, synapses in the heart

adrenaline released from?

adrenal cortex

adrenergic synapses

use norepinephrine or noradrenaline. can be excitatory or inhibitory, both slow and indirect.

serotonin

lack causes depression. antidepressants→ re-uptake of serotonin

dopamine

damage of dopamine-released neurones causes rigidity and stiffness (parkinson’s disease)

reflex

rapid response to a stimulus

endocrine system

lipid soluble or water soluble. only lipid soluble can enter cells without needing a carrier.

classical endocrine hormones

Substances released from one tissue and transported via the bloodstream to a different tissue, resulting in changes to that tissue.

hormone 3 chemical classes

amino acid derivatives, peptides and proteins, lipid derived hormones.

amino acid derived hormones

water soluble, cannot passively diffuse across membranes

peptides and proteins

water soluble, can’t passively diffuse across membranes, fast acting

lipid derived hormones

lipid soluble, can passively diffuse across membranes, slower mode of action

why are lipid derived hormones slower acting?

need to be transported around bound to a water soluble protein, released at a target cell, gain entry to cell, and bind to inside receptor.

hormones with intracellular receptors

slow, but long lasting. steroid & thyroid hormones

hormones with plasma membrane receptors

fast (within seconds). protein, peptide and amino acid hormones.

how does the hypothalamus control endocrine function? (3 ways)

1- secretion of a trophic hormone (releasing hormone)

2- sympathetic system from the medulla

3- production of either Adh or oxytosin

the pancreas

98% exocrine → secrete digestive enzymes and alkaline pacreatic juices to small intestine. 2% endocrine → cells located in islets of langerhans

what are the 4 cell types in the islet of langerhans?

alpha, beta, delta, and F cells

alpha cells

secrete glucagon

beta cells

secrete insulin

delta cells

secrete somatostatin

F cells

secrete pancreatic polypeptide

what does insulin do

acts to lower blood glucose levels

effects of insulin

rapid: increased transport of glucose, amino acids and K+ into insulin sensitive cells

intermediate: stimulates protein synthesis→ inhibits protein breakdown

activates conversion of glucose to glycogen. inhibits conversion of amino acids to glucose.

delayed: increased mRNA for lipogenic and other enzymes

composition of insulin

two chains: A chain is 21 amino acids long, B chain is 30 amino acids long

glucagon effect

raise blood glucose levels by:

1- stimulating gluconeogenesis

2- mobilising liver glycogen

gluconeogenesis

formation of glucose from lactate

glycogenolysis

break down of glycogen to release glucose from the liver

lipolysis

breakdown of fats in adipose tissue (body fat)