M5-commincation and homeostasis Flashcards
define homeostasis
its the maintenance of a constant internal environment
define positive feedback
positive feedback mechanisms amplify a change from the normal level, used to rapidly activate something
why is positive feedback not involved in homeostasis?
it does not keep your internal environment constant
what is a stimulus?
a change in the internal or external environment
what is a receptor?
they detect a stimuli and a re specific
what are effectors?
are cells that bring about a response to a stimulus to produce an effect
what does a sensory neurone do?
transmit nerve impulses from receptors to the CNS
what does a motor neurone do?
transmit nerve impulses from the CNS to effectors
what does a relay neurone do?
transmit impulses between sensory neurones and motor neurone
what is the CNS process?
stimulus - you see a friend waving
receptor - light receptors (photoreceptors) in you eyes detect the wave
CNS - CNS processes information and decides what to do about it
effectors - muscle cells are stimulated by the motor neurones
response - muscles contract to make your arm wave
what do sensory receptors convert stimulus energy to?
nerve impulses
where do axons carry nerve impulses?
Away from the cell body
where do dendrites and dendrons carry nerve impulses?
towards the cell body
what is the structure of sensory neurones?
short dendrites and one long dendron (receptor cells to cell body)
one long axon cell body to CNS)
what is the structure of a motor neurone?
many short dendrites (CNS to cell body)
one long axon (cell body to effector cells)
what is the structure of a relay neurone?
many short dendrites (sensory to cell body)
one axon (cell body to motor)
what does a bigger stimulus cause?
it causes more frequent impulses
what are the synapses called that use acetylcholine?
cholinergic synapses
what is acetylcholine broken down by?
an enzyme called acetylcholinesterase
what happens at the excitatory synapse?
neurotransmitters depolarise the postsynaptic membrane, making it fire an action potential if the threshold is reached
what happens at the inhibitory synapse?
when neurotransmitters bind to receptors on the postsynaptic membrane, they hyperpolarise the membrane (making the potential difference more negative), preventing an action potential from being fired
what is synaptic divergence?
when one neurone connects to many neurones and information can be dispersed to different parts of the body
what is synaptic convergence?
when many neurones connect to one neurone and information can be amplified
why does summation occur?
some stimulus are weak so little neurotransmitter is released into synaptic cleft meaning its not enough to excite the postsynaptic membrane to the threshold level and thus stimulate an action potential so summation can combine the effect of neurotransmitters
what is spatial summation?
when neurones converge
what is temporal summation?
is where 2 or more nerve impulses arrive in quick succession from the same presynaptic neurone
what does the hormonal system send information as?
chemical signals
what are hormones?
chemical messengers
why is hormone a first messenger?
because it carries the chemical message from the endocrine gland to the receptor
why are signalling molecules the second messengers?
they carry the chemical message frim the receptor to other parts of the cell
they activate a cascade inside the cell
what type of hormones does cortex secrete?
steroid hormones
what are 2 examples of steroid hormones?
cortisol and aldosterone
what type of hormone does medulla secret?
catecholamine hormones
what are 2 examples of catecholamine hormones?
adrenaline and noraadrenaline
what is the effect of catecholamine hormones?
increase heart and breathing rate
break down of glycogen to glucose
constriction of blood vessels
what is the effect of steroid hormones?
supress the immune system
increase blood volume and pressure by increasing uptake of sodium ions and water by kidneys
stimulating the break down of proteins and fats, increasing energy available for brain and muscles to respond to the situation
what is the endocrine tissue in the pancreas called?
islet of Langerhans
what do the alpha cells secrete?
a hormone called glucagon
what do the beta cells secrete?
a hormone called insulin
under a light microscope, what colour do the alpha cells appear as?
pink
under a light microscope, what colour do the beta cells appear as?
purple
what is the stain used to differentiate beta and alpha cells?
chrome haematoxylin and phloxine
what are ectotherms?
they cant control their body temperature internally they control their temperature by changing their behaviour
what are 2 examples of ectotherms?
reptiles and fish
what are endotherms?
they control their body temperature internally by homeostasis and they can also control their temperature by behaviour
what are 2 mechanism that mammals do to reduce body temperature?
sweating - more sweat generated by sweat glands, water in sweat evaporates from surface of skin so skin is cooled
vasodilation - arterioles near the surface of the skin dilate, more blood flows through capillaries in the surface layers of the dermis. more heat is lost from skin by radiation and temp is lowered
what are 2 mechanism that mammals do to increase body temperature?
vasoconstriction - arterioles near the surface of the skin constrict so less blood flows through capillaries reducing heat loss
hairs stand up - erector pili muscles contract which makes the hair stand up trapping more air and preventing heat loss
what does the hypothalamus do?
control body temperature
what type of food increases blood glucose concentration?
carbohydrates
what does insulin do?
reduce blood glucose concentration when its too high
what is the process activated by insulin?
glycogenesis
glucose - glycogen
what does glucagon do?
raises blood glucose concentration when its too low
what is the process that is activated by glucagon?
glycogenolysis
glycogen – glucose
gluconeogenesis
glycerol/amino acids to glucose
what is an example of negative feedback?
control of blood glucose
control of body temperature
what is an example of positive feedback
depolarisation
what is type 1 diabetes?
it is an autoimmune disease, where no insulin is produced.
in children/ young adults
what are the treatments for type 1 diabetes?
insulin therapy - regular insulin injections
diet and activity
what is type 2 diabetes?
when beta cells dont product enough insulin or when the body cells dont respond properly to insulin
linked with obesity
what are the treatments for type 2 diabetes?
lifestyle changes so exercise, diet,
medication - metformin ( acts on liver cells to reduce amount of glucose that they release into the blood)
how can stem cells be used to cure diabetes?
they can be grown into beta cells
beta cells will then be implanted into pancreas of a person with type 1 diabetes
person would be able to make insulin as normal
what are the pros for using genetically modified bacteria to make insulin?
cheaper than animal pancreases
larger quantities produced
religious and ethical reasons - pigs and animals
