C3.1 Integration of body systems Flashcards
(from the study guide)
Comparing hormonal and nervous signalling
Hormone signalling: GDRCCCM
- God do repreat can’s country mice
Nervous signalling: CCCS
- can cooks clean sinks
What is crucial to integrate systems
communication between the different components
The difference between unconscious processes and conscious processes
Unconscious processes:
- can happen when asleep
- involunatary
- controlled by the brain and the spinal cord
- glands and smooth muscle are controlled involuntarily
- e.g.: peristalsis (though this is controlled by the enteric nervous system)
Conscious processes
- only happen when awake
- volunatry
- controlled by the cerebral hemispheres of the brain
- striated muscle is controlled voluntarily
- example: chewing food
What acts as the integrating centre for unconscious processes?
- the grey matter of the spinal cord
The pathway how unconscious actions occur
- neurons bring information to the grey matter of the spinal cord and from the sense organs
- interneurons pass impulses via synapses between neurons in the grey matter
- decides the appropriate action for the stimuli
- motor neurons convey signals from grey matter -> muscles and glands
sense organs/receptors -> sense neurons -> interneurons (spinal cord) -> motor neurons -> effectors (for the response)
Why does the spinal cord coordinate unconscious processes
Quicker than conveying signals to the brain
- useful especially in dangerous situations
How does the sensory neuron convey messages from the receptors to the CNS?
- receptor cell detect a change in the external/internal environment*
- receptor cells sends a signal to sensory neurons*
- the sensory neurons convey the impulses to the CNS via the spinal nerves or the cranial nerves (axon)
spinal or cranial depending on where the signal is coming from
- note: for sensory neurons, they have nerve endings that already act as receptors for touch and heat. so in that case, then no need for a receptor cell
Where are the receptor cells located?
- in the skin and sense organs
What do receptor cells do?
Detect changes in the external environment
- e.g. the rod and cone cells in the retina of the eye detect light
From which source does the spinal cord attain sensory information?
- signals from other organs of the body (skin, muscles)
From where does the brain attain sensory information?
- all the signals come from the sense organs on the head: the eyes, ears, nose and tongue
- sensory inputs to the brain are received by specialized areas in the cerebral hemispheres
- for example, the visual cortex receives signals from rod and cone cells
Parts of the spinal cord
Two main tissues:
1.) The white matter
- transmission centre.
- contains axons
- carry impulses to and from the brain
2.) The grey matter
- contains cell bodies of neurons and many synapses
- processing centre for unconscious movements
- decides on the appropriate reaction for the stimuli
Describe the cerebral hemisphere
- part of the brain that plays a major role in conscious movements
- conscious movements -> control of striated muscles
- specifically the motor cortex sends the signals
Striated muscle where is it attached?
To the bone
Wh
What is striated muscle used for?
- to maintain posture
- for locomotion (e.g. standing up)
Overall, how is information conveyed from receptors to the CNS?
How do motor neurons convey messages from the CNS to the muscles?
- the motor neurons receive signals from interneurons from their many dendrites
- one axon leads from the cells body of the motor neuron out of the brain and down the spinal cord
- there, synapse is formed with a second motor neuron whose axon leads to one specific muscle
- the second motor neuron’s axon leads to a specific straited muscle
- then contraction is stimulated once the nerve impulse reaches the end
summary: interneuron -> first motor neuron which has the axon leading out of the brain and down the spinal cord -> the second motor neuron receives the signal via synaptic transmission -> signal sent to the effector for response
Define what a nerve is
- bundle of nerve fibres enclosed in a protective sheath
Which nerve is the widest?
- ## the sciatic nerve is the widest (20 mm across)
Optic nerve
contains up to 1.7 million nerve fibres
How many fibres would small nerves contain
- fewer than a hundred
How many nerves do the organs of the body have
- one or two nerves
Define reflex arc
rapid involuntary response to a specific stimulus
What helps to speed up reflexes?
- reflexes being the simplest type of coordination in the nervous system
- signals pass through the smallest number of neurons
Outline the process of the reflex arc
1. Receptor cells/sensory nerve endings perceive the stimulus.
2.** Sensory neurons receive signals**. Pass them as nerve impulses to the brain or spinal cord via long axons
- The axons end at the interneuron in the grey matter of the spinal cord or brain
3. Interneurons in the grey matter process the signals and make decisions on an appropriate response
4. Motor neurons receive signals via synapses with interneurons. If action potential is achieved, the motor neuron will transmit the signal to an effector
5. Effectors carry out the response after receiving the signal
Describe the cerebellum
- part of the brain
- the coordination center of the brain
- important in: balance, posture, actions that need muscle memopry and the timing of contractions
- BUT does not decide which muscle to contract
How long is a cicardian rhythm?
24 hours
makes sense because it is to be in sync with the day and the night
Describe the superchiasmatic nucleus
- group of cells that set the cicardian rhythm
- controls the secretion of the hormone melatonin by the pineal gland
- a nucleus in the hypothalamus
When is melatonin secretion at its highest and its lowest?
- Highest: during the night
- Lowest: during the dawn
How is melatonin decreased?
- by being “rapidly removed” by the liver
- so blood concentration rise and fall rapidly in response to rate of secretion
The effects of melatonin
- sleepiness or drowsiness (sleep-wake cycle)
- affecting sexual maturation (puberty) by the regulation of the growth hormone
- enhances the immune response of the helper T cells to avoid inflammation (?)
- reduction in urine production
- drop in core body temperature
- decrease in blood pressure
Explain the sleep-wake cycle effect of melatonin
- ^ melatonin = ^ sleepiness
- v melatonin levels = encourage waking at the end of the night
How does the SCN know whether to inhibit or promote melatonin secretion
- by knowing what time of day it is -> by synchronizing with the visible light wavelengths
- a ganglion cell in the retina of the eye detects light in the wavelength of 460-480 nm and passes impulses to cells in the SCN
- signals to SCN the timing of dusk and dawn
- allows the SCN to adjust melatonin secretion so it corresponds to the day-night cycle
Describe epinephrine
- epinephrine is also known as adrenaline
- aka “fight or flight”
- secreted by the adrenal glands
- prepares the body for vigorous activity
Outline the different effects of epinephrine
- striated muscle fibres convert glycogen -> glucose, increasing supplies for respiration
- liver cells do the same and put it into blood transport for the muscles
- broncioles in the lungs dilate/widen -> ventilation ez’ier
- the intercostal muscles and diaphragm contract faster and more forcefully -> a larger total volume of air is breathed in and out per minute*
- sinoatrial node speeds up the heart rate
- arterioles carrying blood to muscles and liver widen/vasodilate
- arterioles carryin blood to the gut, kidneys and skin narrow (vasoconstrict) so less blood to them
- due to the cells in the brainstem that control the ventilation (in the respiratory center)
What controls epinephrine secretion?
- the brain
When does epinephrine increase
it increases when vigorous activity may be necessary (threat or opportunity)
Describe the hypothalamus
- small region of the brain
- major role in the integration of body systems
- links the nervous sustem to the endocrine system via the pituitary gland
- has specialized areas called nuclei which control one or more specific systems
- e.g. superchiasmatic nucleus and the sleep wake syscle
What kind of sensors do the nuclei have?
- blood temperature
- blood glucose concentration
- osmolarity
- concentrations of various hormones
What do the nuclei of the hypothalamus do exactly?
- they direct what hormone would be secreted by the pituitary gland
From where do some of the many nuclei receive signals?
- sense organs either directly or indirectly via the cerebral hemispheres
- other parts of the brain such as the medulla oblongata
How is the hypothalamus and the pituitary gland connected
by a narrow stalk
What are the two parts of the pituitary gland?
- anterior and posterior lobes
- but both secrete hormones into blood capillaries (hypothalamus controlled)
What are the hormones secreted by the posterior pituitary and the anterior pituitary
Posterior pituitary
- antidiueretic hormone (ADH)
- oxytocin
Anterior pituitary
- luteinizing hormone (LH)
- follicle-stimulating hormone (FSH)
Describe how the heart rate is controlled
- the baroreceptor in the walls of the aorta and carotid arteries monitor blood pressure
- the chemoreceptors monitor the CO2, oxygen and pH
- if something is too low or too high, they will send a signal to the cardiovascular centre to stop it (negative feedback)
- the signal will then be send to the sinoatrial node either through the vagus or the sympathetic nerve
- the heart rate either accelerates or decreases
What happens when the heart rate is faster?
- lower CO2 and higher oxygen (because of gas exchange)
- higher pH levels due to lowered CO2
- higher blood pressure
- due to the cardiac output: heart rate x volume of blood being pumped out
What is the normal range for blood pH?
7.35-7.45
kept within this range by negative feedback
At which levels of blood pH is it considered life-threatening?
below 6.8 (acidosis)
What are the causes for higher ventilation rate
- high CO2 levels/low blood pH (to get out the CO2 using gas exchange)
- low oxygen concentration
What are the causes for an increased heart rate
- low blood pressure
- low oxygen concentration
- low pH levels (lots of CO2)
the similarities with the ventilation rate and the heart rate would make it seem that they are two positively correlational? like why when we are nervous, our heart starts to beat fast and we begin to breathe heavily
Describe the control of the ventilation rate
- the chemoreceptors in the walls of the aorta and the carotid arteries monitor blood pH
- the chemoreceptors in the carotid walls monitor the O2 conc.
- if they detect something wrong, they will signal to the respiratory centre in the brain stem to alter the ventilation rate (negative feedback)
- the signals will then be sent to the muscles that are used in breathing to contract *
- then when these muscles contract, signals from stretch receptors indicate it to the respiratory centre
- it will then stop the signals of inhalling and exhaling
- depending on what the signalling is, it would lead to more contractions per period of time or not
Define peristalsis
- wave of contraction and relaxation in the wall of the gut
- moves food from mouth to anus
What are two layers of the gut involved in peristalsis
- both are smooth muscle
- longitudinal muscle (outer)
- the circular muscle (inner)
Describe peristalsis
- The circular muscle behind the partially digested food in the gut contracts to avoid the food returning to the mouth
- the longitudinal muscles shorten to push the food forwards along the gut
What controls the peristaltic muscle contractions in the gut?
the enteric nervous system
Outline two gut movements that are not controlled by the enteric nervous system and are voluntary
- swallowing. tongue initiates it by pushing the food back of the mouth cavity and the tongue is made of striated muscle. tongue is also under control by the brain
- defecation — it is involuntary in babies but voluntary in adults or young children
Describe defecation
- the removal of faeces from the rectum via the anus
- the amus contains a small ring of smooth muscle (ie. the sphincter
- ther wall of the rectum contains layers of circular and longitudinal smooth muscle
- during defecation, the anus relazes and widen and the wall of the rectum contracts
