Indroduction to nervous and endocrine systems Flashcards
what does the nervous system consist of?
The central nervous system and peripheral nervous system
What does the CNS consist of?
- Brain and spinal cord
- voluntary and involuntary control
- behaviour
What does the PNS consist of?
Connects CNS to limbs and organs
Divided into:
ANS - parasympathetic, sympathetic and enteric NS (involuntary)
SNS - voluntary motor control eg. muscle movements
What is an example of the SNS mediating involuntary control?
reflex arcs
What does connection of dendrite and axon terminal form?
synapse
what do oligodendrocytes form?
Myelin - this causes the signal to be quicker (creates protective sheaths around nerve fibres)
what is the function of the cell body of a neuron?
contains genetic information, maintains the neuron’s structure, and provides energy to drive activities.
what is the function of the dendrites of a neuron?
receive input from many other neurons and carry those signals to the cell body
what is the function of astrocytes
clearing excess neurotransmitters, stabilizing and regulating the blood-brain barrier, and promoting synapse formation.
what is the function of the axon?
directs electrical impulses or action potentials away from the cell body or soma of a neuron towards another cell
what are axon terminals?
It is responsible for releasing neurotransmitters and is in close proximity to but not touching other nerves or effector cells, such as muscles.
What happens to synaptic vesicles at the axon terminal?
they are filled with neurotransmitters which are released into the synapse and binds with receptors
What does the blood brain barrier prevent?
Toxic chemicals from getting to the brain
- Prevents 98% of drugs from passing
What do endocrine glands do?
Secrete hormones into the bloodstream
- target cells express hormone receptors
what are different types of hormones?
Peptide
Steroid
Amine
What is an examples of a peptide hormone?
Insulin, glucagon (hydrophilic - can’t cross membranes so are released by exocytosis)
What are examples of steroid hormones?
oestrogen, testosterone (hydrophobic so is able to pass through membranes - typically found inside the cell)
what is homeostasis?
the ability of the body or a cell to seek and maintain a condition of equilibrium or stability within its internal environment when dealing with external changes
what happens when the body temperature increases?
- Blood vessels dilate
- capillaries become flushed with warm blood
- Heat radiates from skin surface
- Sweat glands activated, secrete perspiration to help cool the body
what happens when body temperature decreases?
- blood vessels constrict
- blood diverted from skin capillaries to minimise heat loss from skin
- skeletal muscle activates when more heat must be generated; shivering begins
What happens if calcium levels drop?
parathyroid releases PTH which:
- increases calcium release from bones
- increase calcium uptake in intestines
- increase calcium reabsorption from urine
what is the difference between between the nervous system and endocrine?
- NS is a wired system with arrangement between neurons, ES is wireless with no connection
- Neurotransmitters are released across short distances, hormones are carried long distances in the blood
- NS response is rapid and brief, ES is slow and longer lasting
what is the axon hillock?
has lots of sodium channels for action potentials to fire
what produces myelin sheets?
Schwann cells (PNS)
Oligodendrocytes (CNS)
What is the node of ranvier?
spaces between myelin which allows the action potential to fire
What is found at dendritic spines?
neurotransmitter receptors which cause depolarisation
What are examples of neurotransmitters?
CNS - glutamate, GABA, serotonin, dopamine, noradrenaline
PNS - noradrenaline, acetylcholine
How does resting membrane potential develop?
- Membrane is more permeable to potassium than sodium ions
- inside of the cell becomes negative (more potassium flowing out than sodium moving in)
- resting membrane potential develops
- sodium potassium pumps maintain resting potential
how does the sodium potassium pump work?
There is more sodium outside the cell and more potassium inside the cell
Uses energy in the form of ATP to move ions against their diffusion gradient
3 sodium ions are pumped out of the cell
2 potassium ions are pumped into the cell
What happens if an action potential reaches the threshold
Voltage gated sodium channels open (depolarisation)
what happens during depolarisation?
potassium ions diffuse out of the cell
how does it get back to resting potential after hyperpolarisation?
active transport using sodium-potassium pumps
what is the time when the membrane is hyperpolarised called?
refractory period - no action potentials can occur
What is absolute and relative refractory periods?
During absolute refractory, the neuron cannot fire another action potential. Relative refractory occurs after absolute refractory. During relative refractory, it is possible for the neuron to produce another action potential, but it requires a much greater stimulus to reach the threshold.
What is the effector neurotransmitter for sympathetic and parasympathetic ns
Sympathetic - NA acting on adrenoceptors
Parasympathetic - acetylcholine (Ach) acting on muscarinic Ach receptors
what is the ganglia neurotransmitter?
Ach for both sympathetic and parasympathetic ganglia acting on nicotinic receptors
what is the localisation of ganglia?
Sympathetic- close to spinal cord
Parasympathetic - close or within target organs
what are features of the brain functions?
- four main cells: neurones, astrocytes, microglia ans oligodendrocytes
- consciousness
- behaviour
- learning and memory
-senses
What are features of the spinal cord functions?
- cells types: neurones, astrocytes, microglia, oligodendrocytes
- pathway connecting brain to PNS
- Fibre tracts running to/from brain
- peripheral afferent input via dorsal horn
- efferent input via ventral horn
how many vertebrae does the spinal column have?
31
where does sympathetic interaction in the spinal cord occur?
thoracolumbar
where does parasympathetic innervation in the spinal cord occur?
craniosacral
is glutamate and GABA excitatory or inhibitory?
Glutamate - excitory
GABA - inhibitory
what is IC50 and EC50
50% of max response
- inhibitory conc
-excitory conc
what does the lower the value of IC or EC50 mean?
the more potent the drug
what is chemical antagonism?
when one drug antagonises the action of another by chemically combining with it
what is physiological antagonism?
when two drugs counteract each other by producing opposing effects on different receptors
