unit 4: homeostasis Flashcards
homeostasis
the body’s attempt to adjust to a fluctuating external enviroment
what does homeostasis maintain and how is it achieved
a dynamic equilibrium (balance) as the result of internal control mechs that continuosly oppose outside forces that tend to change the enviroment.
acheived through freedback systems .
negative feedback loop
process that detects and reverses deviations from normal body conditions.
explain a brief overview of the 5 steps of negative feedback loop
stimulus(environmental change)
sensor(eg,free nerve ending in the skin)
integrator (the brain)
effector(a muscle or gland)
response(sysytem output)
in the negative feedback mechanisms, the response of the system cancels or counteracts the effect of the orignal environment change
3 components of homeostasis
a) sensory receptors
b) integrator (coordinating centre)
c) effectors (regulators)
sensory receptors
detects change in an internal condtion and sends nerve impulses to the brain
integrator (coordinating centre)
the brain sends messages to the effectors
effectors(regulators)
cause a change in the internal condtion that returns it to normal
the part of the brain that messages are sent to
hypothalamus
What is the primary function of the kidney?
Filters the blood in order to remove cellular waste products.
The kidneys play a crucial role in maintaining the body’s internal environment by filtering out waste.
What is homeostatic control in the context of kidney function?
Controls water balance, Na+, K+, Co2+, and bicarbonate ions levels in blood.
Homeostasis is vital for maintaining stable conditions in the body.
What hormone does the kidney secrete that stimulates RBC production?
Erythropoietin.
Erythropoietin is essential for regulating red blood cell formation in response to oxygen levels.
What activates vitamin D production in the skin?
The kidney.
Vitamin D is important for calcium absorption and overall bone health.
Fill in the blank: The kidney controls levels of _______ in blood.
Na+, K+, Co2+, and bicarbonate ions.
These ions are critical for various physiological functions including nerve transmission and muscle contraction.
What is the shape and size of the kidneys?
Two bean shaped organs, about the size of a clenched fist
Where are the kidneys located in the body?
Against the dorsal body wall on either side of the spine
What percentage of the blood supply do the kidneys contain at any given moment?
20%
Is it possible for the human body to function with one kidney?
Yes
What happens to the functioning kidney if one kidney is removed?
The operating kidney will increase in size to accommodate the increased workload
What are the three distinct regions of the kidney?
- Cortex
- Medulla
- Pelvis
What is the outer region of the kidney called?
Cortex
What is located beneath the cortex of the kidney?
Medulla
What is the hollow chamber within the medulla called?
Pelvis
How many nephrons are approximately in the cortex and medulla of each kidney?
About 1 million nephrons
What is the structural and functional unit of each kidney?
Nephron
What is the structure of a nephron?
A long tubule enclosed at one end and open at the other
What is the name of the double wall chamber at the closed end of the nephron?
Bowman’s Capsule
What network of capillaries is found within Bowman’s Capsule?
Glomerulus
What are the three distinct parts of the nephron tubule?
- Proximal tubule
- Loop of Henle
- Distal tubule
Where is the proximal tubule located?
Coiled near the Bowman’s capsule
What is notable about the cells of the walls in the proximal tubule?
They are richly supplied with mitochondria
What does the Loop of Henle consist of?
A long thin-walled augment that runs into the medulla, making a hairpin turn and returning up towards Bowman’s capsule
Where does the distal tubule ascend?
Through the medulla to the cortex
What is the primary function of Bowman’s capsule in nephron filtration?
To filter dissolved solutes and water out of blood in the glomerulus into the tubule
Solutes include inorganic ions, glucose, amino acids, and urea. Plasma proteins, RBCs, WBCs, and platelets are not filtered.
Is nephron filtration selective or non-selective?
Non-selective (except by size)
This means that most solutes are filtered regardless of their type.
What does absorption in the nephron involve?
The movement of material from the nephron into the blood
This process is selective for dissolved solutes that the body needs.
Where does selective absorption primarily occur in the nephron?
Proximal tubule
It is permeable to ions, nutrients, and water.
What are the key solutes reabsorbed in the proximal tubule?
- Glucose
- Amino acids
- Bicarbonate ions
- Salts
These are absorbed via active transport.
What is the permeability of the descending limb of the loop of Henle?
Permeable to water but not salt
Water is absorbed passively into the hypertonic renal medulla.
What happens to nephric filtrate in the descending limb of the loop of Henle?
Water is absorbed passively, concentrating the nephric filtrate
This occurs because the renal medulla is hypertonic.
What is the permeability of the ascending limb of the loop of Henle?
Permeable to salt but impermeable to water
Salt is absorbed both passively and actively.
What substances are absorbed in the distal tubule?
- Nutrients
- Glucose
- Amino acids
- Bicarbonate ions
- Salts
Absorption occurs via active transport, and water is absorbed passively.
What is the role of collecting ducts in the nephron?
They are permeable to salt and water
This allows for the final concentration of urine.
What is the process of secretion in the nephron?
The movement of material from the blood into the nephron
This includes the secretion of hydrogen ions and drugs.
What is the flow chart of urine from collecting ducts?
Collecting ducts -> renal pelvis -> ureter -> bladder -> urethra
This pathway represents the final transport of urine out of the body.
What is the functional unit of the nervous system?
Neuron
Neurons are specialized cells that transmit nerve impulses.
List the three types of neurons.
- Sensory neurons
- Interneurons
- Motor neurons
Each type of neuron has a specific role in the nervous system.
What do sensory neurons do?
Sense and relay info from environment to CNS
CNS stands for Central Nervous System.
What is the role of interneurons?
Links neurons within the body
Interneurons are crucial for communication between sensory and motor neurons.
What is the function of motor neurons?
Relay info to effectors to produce a response
Effectors include muscles and glands that carry out responses.
What are the main components of a typical neuron?
- Dendrites
- Cell body
- Axon
These components are essential for transmitting nerve impulses.
How are impulses transmitted in a neuron?
From dendrites to the cell body, then away through the axon
This process is essential for communication between neurons.
How long can neurons survive?
Over 100 years
Neurons have limited capacity for division, which contributes to their longevity.
What is a reflex arc?
Simplest nerve pathway
Reflex arcs allow for quick responses without brain involvement.
Where do reflex responses occur?
At the level of the spinal cord
This allows for faster responses to stimuli.
Describe the pathway of an impulse in a reflex arc.
Travels to spinal cord, crosses to interneuron, then to motor neuron
This direct pathway facilitates rapid responses to stimuli.
What happens to the muscle in a reflex arc?
It contracts to produce the appropriate response
This contraction is an involuntary action triggered by the reflex arc.
What are the two main divisions of the nervous system?
CNS and PNS
CNS: Central Nervous System; PNS: Peripheral Nervous System.
What does the CNS include?
Brain and spinal cord.
What does the PNS include?
All nerves in the body, both voluntary and involuntary.
What is the role of the sympathetic nervous system?
Sets off flight or fight response.
What does the parasympathetic nervous system do?
Reverses the effects of the sympathetic nervous system response.
What happens to the pupils during sympathetic activation?
Dilate.
What happens to the pupils during parasympathetic activation?
Constrict.
What effect does the sympathetic nervous system have on salivary glands?
Stops or decreases secretion.
What effect does the parasympathetic nervous system have on salivary glands?
Increases secretion of saliva.
What happens to bronchioles during sympathetic activation?
Dilate.
What happens to bronchioles during parasympathetic activation?
Constrict.
What effect does the sympathetic nervous system have on heart rate?
Increases heart rate.
What effect does the parasympathetic nervous system have on heart rate?
Decreases/slows heart rate.
What does the adrenal gland secrete during sympathetic activation?
Adrenaline.
What is the effect of the sympathetic nervous system on the stomach?
Decreases secretion of digestive juices.
What is the effect of the parasympathetic nervous system on the stomach?
Increases secretion of digestive juices.
What happens to intestinal motility during sympathetic activation?
Decreases motility.
What happens to intestinal motility during parasympathetic activation?
Increases motility.
What happens to the colon during sympathetic activation?
Retention of contents.
What happens to the colon during parasympathetic activation?
Emptying of contents.
What is the effect of the sympathetic nervous system on the bladder?
Delays emptying.
What is the effect of the parasympathetic nervous system on the bladder?
Emptying of contents.
What effect does the sympathetic nervous system have on glucose release from the liver?
Increase of release of glucose.
What effect does the parasympathetic nervous system have on glucose storage in the liver?
Promotes storage of glucose.
What happens to blood flow in the skin during sympathetic activation?
Increases blood flow.
What happens to blood flow in the skin during parasympathetic activation?
Decreases blood flow.
Resting Membrane Potential:
-70 mV (polarized membrane)
Excited Membrane Potential:
+40 mV
Reason for Charge
Unequal concentration of ions (K+ and Na+) across the nerve membrane.
Why can’t negative ions cross the membrane?
They are too large and remain inside the cell.
What happens to K+ ions at rest?
They diffuse out of the cell (high concentration inside).
What happens to Na+ ions at rest?
They diffuse into the cell (high concentration outside).
Why is the inside of the membrane negative at rest?
The membrane is 50x more permeable to K+ than Na+, so the rapid K+ diffusion causes the interior to lose more positive ions.
What happens during depolarization?
Na+ gates open, allowing Na+ to flow in, causing a charge reversal (action potential).
How does depolarization spread along the neuron?
Depolarization of one membrane part stimulates adjacent areas to depolarize.
What happens during repolarization?
Na+ gates close, and K+ gates restore the resting potential.
How does the Na+-K+ pump restore balance?
actively transports 3 Na+ out and 2 K+ into the cell.
What is the refractory period?
The time needed to re-establish the resting membrane potential.
How long does the refractory period last?
1-10 milliseconds.
How does the impulse travel along a neuron?
As a wave of depolarization followed by repolarization.
What is the threshold level of a neuron?
The minimum stimulus required to produce a response.
What does the all-or-none principle mean?
Neurons fire maximally or not at all, regardless of stimulus intensity above the threshold.
How is the intensity of a stimulus detected?
By the frequency of impulses and the number of neurons stimulated.
Does the strength of an impulse decrease as it travels?
No, it remains constant.
How does the myelin sheath affect impulse transmission?
it increases speed by allowing the impulse to jump between nodes of Ranvier.
What is a synapse?
A gap between neurons where signals are transmitted.
How do neurons communicate across synapses?
Using neurotransmitters like acetylcholine.
What does acetylcholine do?
Opens Na+ channels, triggering depolarization.
What does cholinesterase do?
Breaks down acetylcholine, closing Na+ channels to stop depolarization.
What is grey matter?
Grey matter is the tissue in the brain and spinal cord where cell bodies and dendrites are located. In the brain, grey matter is on the outer layer, but in the spinal cord, it is located in the center.
What is white matter?
tissue made of axons that connect different parts of the brain and spinal cord. In the brain, it is located beneath the grey matter, while in the spinal cord, it surrounds the grey matter.
What are the meninges?
They are three layers that protect the brain and spinal cord.
What is cerebrospinal fluid?
It’s fluid around the brain and spinal cord that cushions them and helps with communication.
What does the medulla oblongata do?
It controls breathing, heart rate, and digestion.
What is the function of the pons?
It links the cerebellum and medulla.
What does the cerebellum do
It helps with balance and movement.
What does the olfactory lobe do?
It processes the sense of smell.
What is the cerebrum?
It’s the largest brain part, controlling movement and senses.
What is the cerebral cortex?
It’s the outer layer of the brain
What is the corpus callosum?
It connects the two brain halves.
What does the frontal lobe do?
It handles memory, attention, and decision-making.
What is the temporal lobe’s job?
It manages senses, emotions, and memory.
What does the parietal lobe do?
It processes touch and combines sensory input.
What is the occipital lobe for?
It’s for vision, including color and motion
What is the thalamus?
It’s a relay station for sensory and motor signals
What does the hypothalamus control?
It controls hunger, thirst, mood, and sleep.
What is the pituitary gland?
It produces hormones for growth and metabolism.
What are the three main layers of the eye?
Outer, middle, and inner layers.
What is the function of the sclera?
Supports and protects delicate photocells.
What does the cornea do?
Refracts light toward the pupil.
What is the role of the aqueous humour?
Supplies nutrients to the cornea and refracts light.
What does the choroid do?
Contains pigments to prevent light scattering by absorbing stray light and includes blood vessels.
What is the function of the iris?
Regulates the amount of light entering the eye.
What does the vitreous humour do?
Maintains the shape of the eyeball and permits light transmission to the retina.
What is the purpose of the lens?
Focuses the image on the retina.
What is the pupil, and what does it do?
The opening in the iris that allows light into the eye.
What is the function of the retina?
Contains the photoreceptors.
What are rods, and what is their role?
Photoreceptors used for viewing in dim light.
What are cones, and what is their function?
Photoreceptors that identify color.
What is special about the fovea centralis?
It is the most light-sensitive area of the retina and contains only cones.
What are the three main sections of the ear?
External ear, middle ear, and inner ear.
What is the pinna, and what does it do?
The outer part of the external ear; it amplifies sound by funneling it from a large area into the narrower auditory canal.
What is the function of the auditory canal?
Carries sound waves into the tympanic membrane.
What are the ossicles, and what is their role?
Tiny bones (malleus, incus, stapes) that amplify and carry sound in the middle ear.
What is another name for the tympanic membrane, and what is its function?
Also called the eardrum, it receives sound waves.
What does the oval window do?
Receives sound waves from the ossicles.
What is the Eustachian tube, and why is it important?
An air-filled tube in the middle ear that equalizes pressure between the outer and inner ear.
What is the vestibule, and what is its function?
A chamber at the base of the semicircular canals; it is concerned with static equilibrium.
What do the semicircular canals do?
Fluid-filled structures that provide information about dynamic equilibrium.
What is the cochlea, and what does it do?
A coiled tube in the inner ear that receives sound waves; its tiny hairs convert them into impulses.
