Flashcards in Module 5 Deck (62)
Describe sensory neurones
Transmit impulses from a sensory receptor to relay neurone, motor neurone or brain.
1 dendron, cell body and 1 axon
Describe relay neurones
Transmit impulses between neurones
Many short axis and dendrons
Describe motor neurones
Transit impulses from really/sensory neurones to an effector
1 long axon and many short dendrites
What happens in the membrane of the sensory receptor in response to pressure
Pascinian corpuscle changes shape
Na+ channels open
Na+ ions enter
generator potential creates an action potential
Outline two roles of synapses in the nervous system.
transmit information between neurones
ensure one way transmission of impulses (unidirectional)
Describe how a resting potential occurs
=Na+ are actively transported out of the axon , K+ actively transported into the the axon by sodium-potassium pumps. (3 sodium for every 2 potassium)
=Na+ diffuse back into, K+ diffuse out of axon down an electrochemical gradient
=However most of the sodium channels are closed and most of the potassium channels are open, allowing potassium out.
=This creates an resting potential of -70mV, with the inside negative to the outside
What is an action potential?
A depolarisation of the cell membrane so it becomes more positive on the inside than outside, creating a nerve impulse
Describe how an action potential is created
-Energy of stimulus triggers some sodium channels to open, making the membrane more permeable to Na+ ions, Na+ diffuse into the axon down an electrochemical (inside is less negative)
-More sodium ion channels open (positive feedback)
-When potential difference reaches +40mV sodium ion channels close and potassium ion channels open (depolarisation)
-Potassium ions diffuse down an electrochemical gradient, causing the inside to become more negative (hyperpolariation) Axon turns to resting potential
What is the refractory period?
A short period of time when the axon can't be excited again
What is saltatory conduction?
Where the action potential jumps from one node to another
What is the all-or-nothing principle?
if the threshold is reached an action potential is always created
What are the 2 types of neurotransmitters?
1 ) Excitatory= result in depolarisation and an action potential if the threshold is reached (e.g.. Acetylcholine)
2 ) Inhibitory= result in hyperpolaristion, prevents action potential (e.g. GABA)
Describe the transmission of impulses across a synapse
-Action potential reaches the end of the presynaptic membrane
-Depolaristion. Calsium channels open and calcium ions diffuse into the presynaptic knob
-Neurotransmitters are release into the synaptic cleft via vesicles by exocytosis
-Sodium ion channels open and sodium ions diffuse into the post synaptic neurone.
-Action potential is created
What is spatial summation?
Where many presynaptic neurones connects to one post synaptic neurone
What is temporal summation?
Where a single presynaptic neurone releases neurotransmitter several times
What is the somatic nervous system?
This system is under conscious control (voluntary)
What is the autonomic nervous system?
This system works constantly and is under subconscious control (involuntary)
What are the 5 main areas of the brain?
Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland
Describe the cerebrum
Controls voluntary actions (e.g. memory)
-Highly convoluted, which increases SA so theres greater capacity for complex activity
Describe the cerebellum
Controls unconscious actions (e.g. balance)
Describe the medulla oblongata
Used in autonomic control (e.g. heart rate)
Describe the hypothalamus
Regulatory centre for temperature and water balance
-controls complex behavioural patterns (sleeping)
-monitors composition of blood plasma
-produces hormone, endocrine gland
Describe the pituitary gland
Stores and releases hormones
What is the adrenal cortex responsible for?
Outer region- produces hormones that are vital to life (glucocorticoids, mineralocorticoids, androgens)
What is the adrenal medulla responsible for?
Inner region- produces non-essential hormones
What are the functions of the pancreas?
Exocrine gland-produces and releases enzymes via a duct
Endocrine gland-produces hormones and releases them into the blood
What is glycogenolysis?
Where glycogen stored in the liver and muscles is broken down in to glucose which is released into the bloodstream (increasing BGC)
What is gluconeogenesis?
The production of glucose from a non-carbohydrate source
What is glycogenesis?
When excess glucose is converted into glycogen and stored in the liver
What is the role of insulin?
Lowers BGC by:
-Increasing rate of absorption of glucose by cells
-Increasing rate of glycogenesis
Increasing respiratory rate of cells
What is the role of glucagon?
Increases BGC by:
-Reducing the amount of glucose absorbed by liver cells
How is insulin secretion controlled?
-At normal BGC, potassium channels in B cells are open causing potassium to diffuse out. Inside at -70mV
-When BGC increases, glucose enters the cell by a glucose transporter
-Glucose is metabolised inside the mitochondria, producing ATP
-The ATP bind to the potassium channels causing them to close. They are ATP-sensitive potassium channels
-potential difference reduces to -30mV and depolarisation occurs
-Voltage gated calcium ions open
-Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis.
What are ectotherms?
most animals are ectotherms and use their surrounding stores warm their bodies.
Invertebrate animals, fish, amphibians and reptiles
What are endotherms?
they rely on their metabolic processes to warm them up
mammals and birds
What is the function of the hepatic artery
brings oxygenated blood into the liver
What is the function of the hepatic portal vein
carries blood loaded with products of digestion from the intestine to the liver
What is the function of hepatocytes
secrete bile from the breakdown of the blood into canaliculi
What is the function of canaliculi
bile drains from the bile ductules which take bile to the gall bladder
What is the function of gall bladder
holds bile from the liver until its needed to digest fatty acids
What is the function of kupffer cells
act as resident macrophages in the liver, ingesting foreign particles and protecting against disease
What is the function of sinusoids
supply hepatocytes with oxygen where blood from the hepatic artery and hepatic portal vein mix
What are the functions of the liver?
Deamination of excess amino acids (the body can't store proteins/amino acids) resulting in the ornithine cycle
Describe the descending limb of the proximal convoluted tubule
upper=impermeable to water
lower=permebale to water, runs through medulla causing sodium and chloride ion concentration to increase
-Filtrate entering is isotonic to blood. As it travels down, water passes out by osmosis down a CG
-Not permeable to odium and chloride ions, no active transport
What is the fluid like at the hairpin in the loop of henle?
Very concentrated and hypertonic to the blood in the capillaries
Describe the ascending limb of the proximal convoluted tubule
lower=permeable to sodium and chloride ions and they diffuse out down a CG
upper=sodium and chloride ions are actively pumped out into the medulla tissue fluid against a CG.
-Impermeable to water, causing fluid in the limb to be dilute
-This is important so that urine is more concentrated than the blood
Describe the distal convoluted tubule
Permeability varies depending on levels of ADH
Lack salt= sodium (+chloride) ions will be pumped out
Water can also leave, concentrating the urine
Describe the collecting duct
Permeability is controlled by levels of ADH, determine how much/little is reabsorbed
What does ADH cause
Permeability of the DCT and collecting duct to increase
More ADH means? Less ADH means?
More=small amount of concentrated urine
Less=large amounts of dilute urine
What is haemodialysis?
Blood leaves patients body from an artery and flows into dialysis machine, where it flows between partially permeable dialysis membranes.
What is peritoneal dialysis?
Done inside the body Using a catheter into the abdomen, takes place across the peritoneal membranes, so that urea and excess mineral ions can pass into tissue fluid and into the dialysis fluid.
Describe primary and accessory pigments
Primary act as reaction centres
Accessory pigments transfer energy to primary pigments
Accessory absorb different wavelengths of light
How is light energy absorbed by photosystems is converted into chemical energy
PS1 and PS11
Electron transport chain
ATP produced by chemiosmosis
Electrons move from PS11 to PS1
Describe the Calvin cycle
Occurs in the stroma
Carbon dioxide fixed by RuBP
Enzyme is Rubisco
Unstable 6C intermediate is produced
Breaks down into 2 molecules of GP
2 TP molecules are formed using ATP and reduced NADP
ATP and reduced NADP from the light dependent reaction
TP regenerates RubP using ATP
TP can be used to form lipids amino acids
What factors affect the rate of photosynthesis?
Light intensity=as it increases, rate of ATP and reduced NADP increases
CO2 concentration=as it increases, the rate of carbon fixation in the Calvin cycle increases, and therefore TP
Temperature= affects enzyme-controlled reaction. Rate increases until enzymes denature.
What happens during glycolysis?
-Two phosphates from ATP attach to glucose forming hexose biphosphate
-Splits into 2 triose phosphates
-Phosphates added forming 2 triose biphosphates
-Dehydrogenation occurs forming 2 pyruvate and 4 ATP (net 2 ATP)
What happens during the link reaction?
-Decarboxylation and oxidation of pyruvate.
-Reduced NAD released
-Acetyl coA formed
What happens during Krebs Cycle?
-Acetyl group combines with 4C to form citrate (6C)
-Decarboxylation and dehydrogenation occurs forming reduced NAD and CO2
-More decarboxylation and decarboxylation regenerating oxaloacetate
What happens at the ETC
-Hydrogen atoms are delivered by FAD and NAD and dissociate into H ions and electrons by chemiosmosis
-Diffuse through through ATP synthase, forming ATP
-Water formed, oxygen final electron acceptor
Describe lactate fermentation
-Pyruvate acts as hydrogen acceptor from NADH, catalysed by lactate dehydrogenase
-Pyruvate converted into lactate and NAD is regenerated
Describe alcohol fermentation
-Pyruvate converted into ethanal by pyruvate decarboxylase
-Ethanal accepts hydrogen ions from NADH becoming ethanol