Nervous System 4- Senses and Reflex Flashcards
Describe the components of Physiological Control Systems
SENSOR (RECEPTOR) -> Afferent Pathway -> CONTROL CENTRE -> Efferent pathway -> EFFECTOR
What connects the afferent and efferent neurone
An interneurone
Which parts of the neurones are located in the CNS
The interneurone and the cell body of the efferent neurone
Describe a reflex arc (Sophie Assults Sam Every Normal Monday)
Sense organ -> Afferent neurone -> Synapse -> Efferent neurone -> Neuromuscular junction -> Muscle
What are reflex arcs?
“In-built” responses which are present from birth. Not under voluntary control
What can generator potentials be stimulated by
Sensory stimulus (e.g. mechanical stimulation)
What does EPSP stand for
Excitatory Postsynaptic Potential
What happens is small transient depolarisations are big enough
They evoke an action potential if they reach the threshold
How do cells communicate with each other
Via synapses
Describe the components of a synapse
Pre-synaptic neurone -> synapse -> post-synaptic neurone
What is convergence
When lots of neurones send signals to one individual neurone
What is divergence
When one neurone sends signals to lots of neurones
What is summation
When signals combine
What are the three types of summation
- Temporal 2. Spatial 3. EPSP-IPSP cancellation
What is temporal sumation
Related to time. Same stimulus over period of time
What is spatial summation
Related to space. If close together only need a few signals from each to reach the threshold
What is EPSP-IPSP cancellation
One causes hyperpolarisation, the other caused depolarisation. They cancel eachother out resulting in no action potential.
What are the two characteristics of receptors
They have high specificity and high sensitivity
What does receptors having high specificity mean
They respond more readily to one particular stimulus (e.g. pressure, temperature)
What does receptors having high sensitivity mean
They are extremely sensitive to a determined stimulus (e.g. olfactory stimulus can respond to a few odour molecules the air)
There is only one type of skin receptor- true/ false
False, there are many different types of skin receptors each with detecting different things and adapting at different rates
What are two effectors
Muscles and glands
What are the two types of effector glands
Exocrine and endocrine
What do exocrine effector glands do
Secrete into the bloodstream
What do endocrine effector glands do
Secrete into a specific place (e.g. salivary)
What does a stimulus do
It causes action potentials along a sensory axon
What is an example of a somatic reflex
The stretch reflex
Describe the stretch relex
Receptors in quadriceps -> CNS -> motor neurones -> flexor contracts and knee moves flicking leg up/ extensor contracts and knee moves flicking leg down
What are the characteristic of a somatic reflex arc
Via the spinal chord, fast
What are the characteristics of a autonomic reflex arc
More interneurones so not as quick as the somatic reflex
What is an example of a autonomic reflex arc
The light reflex
Describe the light reflex arc
- Optic nerve receptors in the retina detect light. 2. Info travels via optic nerve fibres to brain 3. Cranial nerve III from brain to papillary sphincter 4. Papillary sphincter = either contract or dilate iris
What does an increase in arterial pressure result in
increase in firing of baroreceptors -> increase in parasympathetic outflow to heart & decrease in sympathetic outflow to heart, arterioles, veins
Reflexes are under voluntary control- true/ false
FALSE, reflexes are not under voluntary control and most are present from birth
