Nervous system Flashcards
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What is Dale’s Law?
states that each neuron has a specialised chemical
what is the difference between a phase and tonic response to a stimulus?
A phase response is a onetime reaction to a stimulus while a tonic response repetitively fires until stimulus is no longer present
What is a resting potential and voltage gradient which chemical channels help to maintain?
Na and K ion channels are abundant in neurons/axons
K moves freely through channels (following gradients) while Na is closely regulated, the Na-K exchange pump costs 1 ATP, which is used for maintaining a resting potential just in case of use - not cost-effective.
Cl and Ca are also important to the electrochemical gradient
What is the voltage of a stimulus, threshold and peak of an action potential of a synapse?
Stimulus -70
Threshold -55
Action potential +40
What is a local/graded potential?
A slight change in voltage, opening a gate due to the presence of a stimulus, can fail or add up to action potential
What ion enters during the depolarisation phase?
Na+
What ion is pumped out during repolarisation phase?
K+
What happens during the hyperpolarisation phase?
Dips below the stimulus voltage to ensure uni-directional movement
What is the final phase of the action potential?
Where the resting potential is re-established at -70
What is the autoimmune disease that is associated with the loss of myelin
Multiple sclerosis
What kind of layered cell membrane are myelin sheaths made from?
glial cell membrane
What do Nodes of Ranvier help with?
Increasing the speed at which voltage is transmitted down axons
What are the features of a synaptic site
The presynaptic axon with synaptic vesicles, the synaptic cleft gap, the postsynaptic cleft containing receptor proteins
What happens in a synapse when the action potential arrives?
Vesicles fuse with terminal membrane producing exocytosis of transmitter (moving a larger molecule from inside to the exterior of the cell). Na+ and Ca^2+ enter channels at this point. Transmitter binds to postsynaptic receptor proteins; ion channels open (Na+). Fused membrane is recycled.
What role do voltage gated calcium channels located in the presynaptic terminal play in APs?
They stimulate the release of transmitters from intracellular vesicles
What is Ionotropic receptor signalling?
A fast form of signalling in the post-synaptic neuron. neurotransmitter bind directly to the channel protein, allowing ion to flow across. e.g Ligand gated ion channel
What is metabotropic receptor signalling?
A slow form of signalling in the post-synaptic neuron. Neurotransmitter bind G protein-coupled receptor, G protein is activated and moves to adjacent ion channel. Channel opens and ions flow through over a longer period of time.
What does the hypothalamus regulate?
Endocrine regulation, autonomic regulation and limbic function
What is encephalisation?
the comparison of cortical regions suggesting higher evolution, bigger cortex
What is telencephalon?
Cortex and deep structures of cerebrum
What is the Diencephalon?
thalamus and hypothalamus
What makes up the brain stem
Mesencephalon midbrain pons and medulla oblongata
What is the brain area behind the brainstem?
Cerebellum
What is the liquid called that surrounds the brain?
Cerebrospinal fluid (CSF) , insulates the brain
What are the 3 protective measures surrounding the brain?
Skull, CSF and meninges
What is the meninges?
Three layers of membranes that cover the brain
What does the blood barrier do?
Ensures only essential molecules such as glucose and oxygen pass into the brain
What does the autonomic system control?
visceral activities such as thermoregulation, digestion, circulation etc. The sympathetic and parasympathetic system work to retain homeostasis
Describe preganglionic nerve connections of the autonomic pathways
sympathetic reside in spinal cord (thoracic and lumbar); parasympathetic originate in brain and lower spinal cord.
What do the preganglionic fibers in the (para)sympathetic autonomic pathways secrete?
Both secrete acetylcholine
What do the postganglionic fibers in the sympathetic autonomic pathways secrete?
norepinephrine and are adrenergic fibers
What do the postganglionic fibers in the parasympathetic autonomic pathways secrete?
acetylcholine and are cholinergic fibers
What are the 2 different structures that make up the adrenal gland?
the cortex and medulla
Adrenal medulla unique because it is ‘postganglionic-like’.. explain..
it secretes both epinephrine and norepinephrine (adrenaline)
What do zonas in the adrenal cortex secrete?
mineralcorticoids and glucocorticoids (cortisol and aldosterone)
How is blood supplied to the brain?
by 2 pairs of arteries:
-Internal Carotid Arteries (ICA)
(anterior 2/3 of brain)
-Vertebral Arteries
(posterior 1/3 of brain)
Branches from both join to produce the Circle of Willis which sits underneath the brain
Why is the circle of Willis important?
It allows blood to access all of the brain in case of a blockage.. buying some time. In the event of a stroke it takes 4-6 minutes for irreversible brain damage to occur.
What is an Ischemic stroke?
Where there is a blockage of a vessel supplying brain
What is a Haemorrhagic stroke?
When blood vessels supplying the brain leak or rupture,
-Intercerebral, bleed within brain
-Subarachnoid, bleed surface of brain
Which system does the endocrine system communicate with?
CNS using bi-directional communication
What can the endocrine system influence in the CNS
sensory and motor systems, leading to behavioural effects which can influence other systems.. feedback. The neuroendocrine system
What is an example of an excitatory neurotransmitter
glutamate
What is an example of an inhibitory neurotransmitter
GABA
what does the neuroendocrine cell do?
CNS cell releases hormones into the bloodstream to act on target cells, could be anywhere. Endocrine cells are specialised for synthesis, storage and release, have highly vascularised tissue
Where are receptors for hormones located (relating to the endocrine system)
cell membrane or cytoplasm
What glands in the CNS does the endocrine system use?
hypothalamus, pituitary and pineal
Which glands in the body does the endocrine system use?
Thyroid, pancreas, adrenal and gonads
What is the function of the hypothalamus?
Controls homeostasis and many body systems such as sexual behaviour, energy balance.
Has different areas with distinct functions, most communicate with the endocrine system through the pituitary gland
Where are neuroendocrine cells located and what do they do?
From hypothalamic nuclei into the median eminence in the anterior pituitary gland. They release neuropeptide hormones into the hypophyseal portal vasculature.
What do neuropeptides stimulate (or inhibit)?
The release of hormones from the pituitary into circulatory system
What are some examples of hormones released by the anterior pituitary gland in response to neuropeptides?
Gonadotropin Releasing Hormone (GnRH) triggers Luteinizing Hormone (LH) and follicle Stimulating Hormone (FSH) release.
Where do neuroendocrine cells project to the posterior pituitary from?
The paraventricular and supraoptic nuclei
where are neuropeptide hormones released into within the posterior pituitary
circulatory system
What are the 2 neuropeptides from the posterior pituitary?
Vasopressin (water balance and blood pressure)
Oxytocin (lactation and uterine contraction)
What is progesterone and what sex has it?
Progesterone released from the corpus luteum has an inhibitory effect on release of FSH and LH through a feedback cycle. It is present in female systems and helps regulate menstruation and pregnancy.
What does oestrogen do in the female neuroendocrine-gonad feedback cycle?
Oestrogen switches from negative to positive feedback mid-cycle to promote release of LH
Where are testicular Leydig cells found?
between seminiferous tubules
What is testosterone produced in response to in Leydig cells
LH binding to receptors on cell membrane
What cells within seminiferous tubules respond to FSH?
Sertoli cells which stimulates sperm maturation
What does FSH stimulate in the ovaries?
Follicle maturation
what is a mature follicle?
A follicle contains an egg in the ovaries. They have layers which secrete hormones, these work on a feedback switch
What do Theca cell produce?
androstenedione
What do Granulosa cells produce?
Oestrogen
What does TSH released by the anterior pituitary stimulate the release of in the thyroid gland?
Triiodothyronine (T3)
Thyroxine (T4)
What does the adrenal cortex respond to from the anterior pituitary?
ACTH (adrenocorticotropic) which is released from corticotrope cells (triggered by Corticotropic Release Hormone CRH)
Where is melatonin produced?
Pinealocytes (which are derived from photoreceptors, making them light-sensitive) found in the pineal
What are melatonin levels like during the day?
Low levels in the CSF during the day
How does Oxytocin work and what does it do?
It is a neuroendocrine reflex, meaning it is produced in response to brain activity due to a stimuli. It induces myoepithelial cells to contract leading to milk ‘letdown’ (not production)
What is cholesterol the major precursor for?
steroid hormones
What enzyme do ovaries need to produce oestrogen from testosterone?
Aromatase
What is the difference between hormone receptors in the membrane and inside of the cell?
Hormone binds with membrane receptor leading to enzyme activation.
Hormone passes through membrane, binds to receptor, then enters the nucleus and stimulates gene transcription
Where is the adrenal medulla located?
On top of the kidneys
What is the stress response?
Hypothalamus produces corticotropin-releasing hormone which releases adrenocorticotropic hormone from the pituitary gland. This progresses to the adrenal gland where the cortex releases glucocorticoids and the medulla which releases epinephrine and norepinephrine
What is an example of a long-term impact of stress?
Can inhibit wound healing
How is cortisol involved in stress arousal?
It is released after adrenaline to maintain high alert and encourage glucose release
What is the Suprachiasmatic Nucleus (SCN)
A specialised group of hypothalamic cells
Receives info about light exposure from ganglion cells in retina (along retinohypothalamic tract)
Activates melatonin secretion by pineal gland.
Circadian pacemaker
Despite SCN clock cells act in a synchronised fashion, each cell appears to have its own..
clock
What are acute and chronic stress responses?
