Homeostasis Flashcards
1
Q
What is homeostasis in the body?
A
- the maintenance of a steady state
- Living systems respond to stress from
External environment: changes in temp. food light etc.
Internal environment: changes in water, waste, food, aging, etc.
To maintains homeostasis
- Stimulus –> receptor –> regulator –> effector
2
Q
Systems specifically involved in homeostasis
A
- Endocrine system (glands and hormones)
- Nervous system (central and peripheral)
these help to coordinate communication - Excretory system (kidneys)
3
Q
What does the endocrine system do?
A
secretes hormones tat coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior.
4
Q
What does the nervous system do?
A
conveys high-speed electrical signals along specialized cells called neurons, these signals regulate other cells.
5
Q
Endocrine signaling
A
Hormones secreted into extracellular fluids by endocrine cells reach their targets via bloodstream.
Endocrine signaling maintains homeostasis, mediates responses to stimuli, regulates growth and development.
6
Q
Local regulators
A
Molecules that act over a short distance, reach target cells solely by diffusion
Paracrine Signaling: the target cells lie near the secreting cells
Autocrine signaling: the target cell is also the secreting cells
7
Q
Synaptic signaling
A
Neurons form specialized junctions with target cells, called synapses.
At synapses, neurons secrete molecules called neurotransmitters that diffuse short distances and bind to receptors on target cells.
8
Q
Neuroendocrine signaling
A
specialized neurosecretory cells secrete molecules called neurohormones that travel to target cells via the bloodstream.
9
Q
Endocrine vs Exocrine glands
A
- Endocrine cells are grouped together in ductless organs called endocrine glands
- Exocrine glands have ducts and which secrete substances onto body surfaces or into cavities.
10
Q
What is the hypothalamus?
A
A region in the brain responsible for coordinating many nerve and hormone functions, including temperature regulation.
11
Q
Cells of the nervous system:
A
Neurons: basic structural and functional units of the nervous system
- respond to stimuli, conduct electrochemical signals and release regulating chemicals
- neurons are organized into tissues called nerves
Glial cells: support neurons by nourishing them, removing wastes, and defending against infection
- they also function as structural support cells
12
Q
Explain structure of neuron: 5 parts
A
Dendrites: projection of cytoplasm that carries impulses towards the cell body are numerous and highly branched- increase SA to receive info.
A cell body: contains the nucleus and is the site of the cells metabolic reactions.
An axon: conducts impulses away from the cell body
Myelin sheath: insulated covering over axon of a nerve cell. Speeds up the rate of impulse
Nodes of Ranvier: regularly occuring gaps between sections of myelin sheath along the axon where nerve cells are transmitted.
13
Q
How to classify a neuron- 3 things
A
Neurons are classified based on the number of processes that extend from the cell body
Multipolar: has several identities, has single axon. Found in the brain and spinal chord.
Bipolar: has a single main dendrite. has a single axon. Found in the inner ear, the retina of the eye, and the olfactory area of brain –> scent detection.
Unipolar: has a single process that extends from the cell body. Dendrite and axon are fused. Found in the peripheral nervous system.
14
Q
Classifying neurons based on function- 3 kinds
A
Sensory neurons: sensory receptors receive stimuli and form nerve impulse. Sensory neurons transmit impulses from sensory receptors to the CNS (central nervous system).
Interneurons (relay neurons): carry impulses within the CNS and act as a link between the sensory and motor neurons.
Motor neurons: transmit information from the CNS to effectors. Effectors include muscles, glands, and other organs that respond to impulses from motor neurons.
15
Q
What is the reflex arc?
A
Some neurons are organized to enable you body to react rapidly in times of danger, even before you are consciously aware of the threat.
A simple connection of neurons that result in an involuntary reflex action in response to stimulus
16
Q
What is resting membrane potential?
A
Resting membrane potential: is the potential difference across a membrane in a resting neuron (about -70mV). It provides energy for generating a nerve impulse.
17
Q
How is resting membrane potential established? -Polarization
3 factors
A
- the sodium/potassium pump
- most important factor that contributes to the resting membrane potential
- uses ATP to transport 3 sodium ions (Na+) out of the cell and 2 potassium ions (K+) into the cell.
- overall result is constant membrane potential of -70mV - Potassium (leak) channels
- more leaky than sodium channels
- some of the potassium ions that were pumped in are allowed to leak out (down concentration gradient), but not many sodium ions can enter. - Large negative charge inside the cell
18
Q
What is action potential?
A
When a neuron send information down an axon, away from the cell body
- all or none phenomenon
- if a stimulus causes the axon to depolarize to a certain level ( the threshold potential), an action potential occurs.
Threshold potentials: close to -50mV
19
Q
Explain the process of action potential-4 steps
A
- Action potential is triggered when the threshold potential is reached. Voltage gated Na+ channels open.
- Na+ ions move down their concentration gradient and rush into the axon causing depolarization of membrane. The membrane potential difference is now +40mV
- Voltage-gated Na+ channels close at +40mV and voltage-gates K+ channels open. Now potassium ions move down their concentration gradient, and the axon causing membranes to be hyperpolarized to -90mV.
- Voltage-gated K+ channels close. The Na+ K+ pump and naturally occuring diffusion restore to the resting membrane potential of -70mV. Membrane is repolarized.
20
Q
What is the central nervous system? (CNS)
A
- The structural function center for the entire nervous system.
- It is the site of neural integration and processing.
- It receives sensory information, evaluates information, and initiates outgoing responses.
21
Q
White matter vs grey matter
A
Myelinated neurons make up white matter,
Unmyelinated neurons make up grey matter
22
Q
What is the spinal chord? 2 nerves found in spinal chord.
A
A column of nerve tissue that extends out of the skull from the brain and downward through a canal within the backbone.
It is the primary reflex center. The tissues are surrounded by cerebrospinal fluid, soft layer tissue, and the spinal column (vertebrae).
Sensory (body–>brain)
Motor (brain–>effector)
both of these nerves found within the spinal chord.
23
Q
The brain, what is it? (and 3 parts that make it up)
A
A complex center that maintains homeostasis.
Protected by the skull and the meninges.
Brain is divided into 3 main parts:
1. Hindbrain
2. Midbrain
3. Forebrain
24
Q
What is the blood brain barrier?
A
Formed by glial cells, and blood vessels.
It separates the blood from the CNS and controls the entrance of substances to the brain from the blood.
Oxygen and glucose constantly cross the blood brain barrier because the brain needs them to function.
25
What is the cerebrospinal fluid, and what does it transport?
- clear liquid derived from blood plasma that circulates throughout the spaces within the brain and spinal chord.
- Transports hormones, white blood cells, and nutrients across the blood brain barrier to the cells of the brain.
- acts at shock absorber, by circulating through layers of meninges
26
What does the Hindbrain do and what parts does it contain?
- Controls homeostasis and coordination
- Cerebellum
- Medulla
- Pons
27
Cerebellum (which main area of brain is it from + functions)
- Hindbrain
- Control homeostasis and coordination
- A cerebellum (little brain): walnut shaped structure is involved in unconcious coordination- posture, reflexes, fine voluntary skills
- Receives sensory information from balance receptors in inner ear + receptors from touch etc.
28
Medulla (which area of the brain is it from + functions)
- Hindbrain
- Connect the brain and spinal cord at the base of the brainstem
- Coordinates many reflexes- automatic bodily functions, maintain homeostasis- including heart rate, breathing etc.
29
Pons (which area of the brain is it from + functions)
- Hindbrain
- Mass of fibres in the brainstem
- Relay center
30
Forebrain (what is it and what parts does it contain?)
- Perceives thought, learning, and emotion
- Hypothalamus
- Cerebrum
- Thalamus (don't need to know)
31
What is the hypothalamus? (which part of brain is it from)
- Forebrain
- Hormone production and maintains homeostasis
- connects nervous system to the endocrine system
32
Structure and function of the cerebrum
- Forebrain
- Outer covering is called cerebral cortex
- responsible for memory, personality, vision, conscious thought, and emotion
- Right and left halves are linked by the corpus callosum, send messages from one half to other
33
The cerebral cortex (what are the lobes (4) for?)
Frontal lobes: thinking, personality, and memory
Parietal lobes: process sensory information from the skin.
Occipital lobes: analyze visual information.
Temporal lobes: mainly process auditory information.
34
What does the peripheral nervous system do?
- Connects CNS to to organs limbs, etc, carrying sensory and motor info
- Allows brain and spinal chord to receive and send info to body
- Regulates involuntary body function, breathing, heartbeat
35
What is the somatic system and what does it do?
- Controls the voluntary movement of skeletal muscles, its neurons serve head, trunk, and limbs
- Includes cranial and spinal nerves, all are myelinated, and contain sensory and motor neurons.
36
What is the autonomic nervous system and what does it do?
Part of autonomic nervous system
- Controls the involuntary glandular secretions
- Maintains homeostasis by adjusting to body's needs without the individual having to think about it.
- Controlled by the hypothalamus, and medulla oblongata
- Further divided into sympathetic and parasympathetic nervous systems
37
Sympathetic nervous system
Part of autonomic nervous system
- Typically activated in stressful situations
- Referred to as "fight or flight"
- Sympathetic neurons and adrenal glands typically activated in stressful situations release epinephrine and norepinephrine
38
Parasympathetic nervous system
- Activated when the body is at rest and calm
- Acts to conserve energy
- Referred to as "rest and digest" response
- Uses the neurotransmitter acetylcholine to control responses
39
What are hormones?
- Produced by an endocrine gland and secreted into the bloodstream
- Exert their effects on a part of the body far away from the cell that secreted it
- Required in very small amounts
- Act upon specific target cells that bind to the appropriate receptor proteins
40
What are the three chemical processes of hormones?
1. Polypeptides (proteins and peptides)
2. Amines Hormones derived from amino acids
3. Steroid hormones
- Lipid soluble hormones (steroids) pass easily through easily through cell membranes, while
Water soluble hormones (polypeptides and amines) do not
- The solubility of a hormones correlates with the location of receptors inside or on the surface of target cells.
41
About feedback regulation (negative and positive feedback loops)
A negative feedback inhibits the actions of the initial stimulus, thus preventing excessive pathway activity
COUNTERACTS THE STIMULUS
A positive feedback reinforces response to stimulus to produce an even greater response.
ex. in mammals oxytocin causes the release of milk, causing greater suckling by offspring which stimulates the release of more oxytocin
INCREASES THE STIMULUS
42
Hypothalamus and pituitary (the hormones produced work in two ways)
Direct- hormone directly stimulates a part of the body, such as muscle and bone growth, and milk production.
Tropic- hormone that regulates hormone production of other glands in the body such as the adrenal cortex, thyroid gland, and gonads.
43
What is the pituitary gland?
- Often called the master gland
- Is located just below the hypothalamus
- Releases important hormones, many of which control other glands in the body
- Connected to the hypothalamus by the pituitary stalk
- Has two lobes; posterior pituitary and anterior pituitary
- Communicates to the hypothalamus through nerves in the pituitary stalk
44
What is the posterior pituitary? (also ADH and oxytocin)
- A collection of nervous tissue- an extension of the hypothalamus
- does NOT produce hormones itself
- Acts more as a storage and release site for 2 hormones, produced by hypothalamus
ADH (anti-diuretic hormone)- stimulates the kidneys to retain water
Oxytocin- involved in uterine contractions, and milk release from mammary glands
45
What is the anterior pituitary?
- connected to the hypothalamus by the hypophyseal portal vessels (a capillary in pituitary stalk)
- Synthesizes and secretes 6 major hormones
- Controls secretions of the thyroid, the adrenal cortex, mammary glands, ovaries, and testes.
46
What is the human growth hormone (hGH) and what does it do?
Too much of too little
- Anterior pituitary gland regulates this hormones
- Affects almost every body tissue by direct stimulation via tropic effects
Growth factors from the liver and hGH increase the following processes:
- Protein synthesis
- Cell division and growth
- Metabolic breakdown
- hGH stimulates the growth of muscles, connective tissue and growth plates on boned
Gigantism- caused by excess amounts of hGH from the pituitary during childhood
Acromegaly- caused by excess amounts of hGH from the pituitary during adulthood
Pituitary dwarfism- caused by insufficient hGH production in childhood
47
What is prolactin and Oxytocin?
Prolactin
- produced in the anterior pituitary gland
- function: to aid in milk production
Oxytocin
- produced by the hypothalamus and stores in the posterior pituitary
- Function: to help with breastfeeding and uterus contractions during labor
the levels of these are quite low outside of pregnancy and breastfeeding
48
Adrenal glands- What are they and what happens to your body when you experience stress?
- the endocrine system helps you cope
- the stress response includes many interacting hormones pathways, including those that regulate, breathing, heart rate, and metabolism
Adrenal glands- pair of organs involved in regulating stress response and blood sugar levels, each gland--> 2 layers
inner later- adrenal medulla
outer layer- adrenal cortex
each layer produces individual hormones and functions differently
49
The Adrenal Medulla- What is it? What does it do?
- Secretes 2 hormones
- Epinephrine (adrenaline)
- Norepinephrine (noradrenaline)
- these hormones regulate short term stress response (fight or flight)
- response to stress: neurons in symp. NS carry signal from hypothalamus to adrenal medulla
50
Functions of Epinephrine and Norepinephrine
- Trigger the release of glucose and fatty acids on the blood
- Increase oxygen delivery to body cells
- Direct blood toward heart, brain and skeletal muscles and away from skin, digestive system, and kidneys
The release of these hormones occurs in response to involuntary sympathetic signals
51
Effects of Epinephrine and Norepinephrine on the body, generally
- Different hormones can have diff effects on diff tissues depending on type of receptor they bind to.
52
The Adrenal Cortex- What is it? What does it do?
- Produces stress hormones that trigger the long term stress response
Hormones are:
- Glucocorticoids (increase blood sugar, metabolism and suppress immune function)
- Mineralocorticoids (affect salt + water balance to increase blood pressure)
- the main mineralocorticoid is Aldosterone: stimulates the kidneys to increase the absorption of sodium in the blood, which raises blood pressure (water follows sodium-osmosis)
- Gonadocorticoids (sex hormones e.g. testosterone)
also
- Cortisol (regulates long term stress response
53
How does Cortisol work and where does it come from
- Comes from the Adrenal Cortex
- Regulates long term stress response
- They hypothalamus secretes a releasing hormone (CRH), which stimulates the anterior pituitary gland to secrete adrenocorticotropic hormone (ACTH)
- ACTH then targets adrenal cortex which causes the secretion of cortisol
Cortisol
- promotes the breakdown of fats and muscle to increase blood glucose levels
- is an anti-inflammatory immune system suppressant
- is controlled in a negative feedback loop, however chronic high levels can cause bad things and early death
54
Thyroid Gland- What is it? What hormones are produced?
- Located below the Larynx
- Is composed of 2 lobes
Hormones produced:
- Thyroxine (T4)
- Triiodothyronine (T3)
secreted by follicular cells
- Calcitonin (less used)
secreted by parafollicular cells
55
What is TSH
- Thyroid Stimulating Hormone
- Released by the anterior pituitary gland and released into the bloodstream
56
What are the actions/affects of Thyroid hormones?
- Impact metabolic rate
- Hormone enters the cell, goes to nucleus , changes gene expression to increase metabolic rate
- Stimulates diverse metabolic activities in many tissues causing an increase in metabolic rate in the body: rate of cellular resp goes up
- Downside to this is that there is an increase in body heat production due to increased oxygen consumption
57
What happens (disease) when you have too much or too little of a thyroid hormone?
Hypothyroidism:
- when the body produces low levels of hormones
- Eg. 1 Hashimotos disease- autoimmune disorder where the body's immune system attacks thyroid
- Eg. 2 Iodine deficiency- caused by lack of iodine in the diet. Thyroid tries to produce more hormones but can't- production of goitre
Hyperthyroidism
- when the thyroid produces too much hormones
- Eg. Grave's disease
Goitre- swelling of thyroid during hypo or hyper
58
What is the function of Calcitonin?
- removes calcium from the blood by increasing uptake of calcium by the bones
- calcium is a vital mineral in the body facilitates muscle contraction, skeletal development
59
What are the parathyroid glands? What is PTH? About negative feedback loop.
- small, circular structures that are responsible for calcium homeostasis
- monitor and regulate calcium blood levels
- able to regulate and control through synthesis and controlled secretion of parathyroid hormone (PTH)
PTH
- the most important regulator of calcium
- parathyroid glands are are able to monitor the concentration of calcium in the bloodstream through the calcium-sensing receptor (CaSR)
- if you don't have enough calcium in the blood, PTH is released (effects of it increase level of calcium in bloodstream
- creates negative feedback loop
1. Release of Ca2+ from bones
2. Higher reabsorption of calcium from urine
3. Stimulate production of vit D (increase calcium absorption in the intestines) in the kidney
60
Function of kidneys with PTH
Function I: PTH works in the thick ascending loop of Henle, distal tubule, and collecting ducts to increase calcium reabsorption.
- Calcium is against its concentration gradient with it enters the cell so sodium-calcium exchangers and ATP-dependant calcium pumps are used to get it into the blood
61
What is the pancreas?
- located on the right side of the abdomen
- has both exocrine and endocrine functions
- plays the main role of maintaining blood sugar levels in the endocrine system
62
What are the Islets of Langerhans in terms of the pancreas?
- 95% of the pancreas consists of exocrine tissue that secretes enzymes that aid in digestion
- remaining 5% left is the endocrine tissue that produces hormones
- endocrine tissue consists of Islets of Langerhans- they have 3 types of cells: alpha, beta, and delta- each type secretes different hormones.
63
What is insulin? How does it work?
- secreted by the beta cells when the pancreas detects a rise in blood sugar level
- a peptide hormone. A chain and B chain held together by 2 disulfide bonds
- when you eat a meal it is broken down into sugars that are absorbed into the bloodstream, the pancreas detects the rise of sugar in the blood and releases insulin
- insulin increases the uptake of glucose from the blood into the cell, promotes formation of glycogen and lipids for long term energy
64
Insulin and target cells, also what is glucagon?
- cells contain insulin receptors that the insulin will bind to, then GLUT4 molecules are stimulated and provide a channel for glucose to enter the cell
Glucagon is another peptide hormone secreted by the pancreas
- target tissue is the liver
65
How does glucagon work?
- When blood glucose levels fall, the alpha cells secrete glucagon, promoting the breakdown of glycogen into glucose to be released into the bloodstream
66
Negative feedback loop of the pancreas (insulin and glucagon)
Insulin
- eat food and blood sugar rises
- pancreas detects this, beta cells secrete insulin to lower it
- once it reaches homeostasis it stops
Glucagon
- blood glucose level falls
- alpha cells secrete glucagon into bloodstream, raising levels
- once homeostasis is reached it stops
67
Type 1 diabetes:
- pancreas doesn't produce enough insulin --> high blood pressure
- state is called hyperglycemia
- no cure
- treatment is for managing blood sugar levels
- caused when the immune system unintentionally destroys the islets in the pancreas
68
Type 2 diabetes:
- inability of a body's cell to respond to insulin as they should
- poor circulation and high blood pressure, damages nerves and lining of small blood vessels
69
Negative vs Positive feedback systems
Negative
- Inhibits a response by reducing the initial stimulus
thus preventing excessive pathway activity
- Endocrine system
- Nervous system
Positive
- uncommon in the human body
- reinforces strengthens the stimulus or change
70
Hormones produced by the pituitary gland
FLAT PEG
- FSH (follicle-stimulating hormone)
- LH (luteinizing hormone)
Goes to the gonads (testicles, ovaries) to signal production of testosterone, sperm, estrogen, progesterone, and regulate the ovarian cycle.
- ACTH (adrenocorticotrophic hormone)
Stimulates the adrenal cortex in to secrete cortisol which promotes the breakdown of fats and muscle proteins.
- TSH (thyroid stimulating hormone)
Stimulates the thyroid gland to secrete thyroxine and triiodothyronine
- Prolactin (only made when PIF is not being released)
Stimulates milk production
- Endorphins (dont need to know)
- GH (growth hormone)
Affects almost every tissue in the body, but mostly stimulates the muscles and bones to grow
71
Key terms for the male reproductive system: Gonads, Gamete, Sex hormone
Gonads: organ that produces reproductive cells (gametes) and the testes produces sperm
Gamete: a reproductive (sex) cell. In males; sperm
Sex hormone: control the development and function of the reproductive system or secondary sex characteristics
72
What is testosterone in terms of the male reproductive system?
- promotes sperm formation and development of the male secondary sexual characteristics
Penis: the primary reproductive function is to transfer sperm from the male to the female reproductive tract
73
What are all the hormones produced in the male reproductive system?
GnRH (Gonadotropin)
- acts on the anterior pituitary gland for it to release 2 different sex hormones which are the lutenizing hormone (LH) and folicle stimulating hormone (FSH)
FSH (Follicle stimulating hormone)
- stimulates the development of sex organs and gamete production on both males and female
Luteinizing hormone (LH)
- stimulates the release of testosterone in the testes
Inhibin
- On the anterior pituitary, to inhibit the production of follicle stimulating
- Results in a negative feedback loop that controls the rate of sperm formation
Testosterone
74
General points about puberty (male)
- Series of hormonal effects that lead to slow changes which includes the development of sex organs and secondary sex characteristics
- begins when the hypothalamus increases GnRH production
75
Gametogenesis and Spermatogenesis (male)
Gametogenesis: the process in which cells undergo meiosis to form gametes
Spermatogenesis: development of sperm. Millions are produced, takes about 7 weeks to develop
76
Negative feedback loop (male)
- Maintains the level of sperm production over time and maintains the secondary sex characteristics
- LH causes the interstitial cells in the testes to secrete testosterone- promotes muscle growth etc. Testosterone acts on the anterior pituitary to inhibit the release of LH. This feedback loop maintains tesosterone.
77
What are the hormones produced in the female reproductive system?
GnRH
- produced by hypothalamus
- when it circulates the blood- causes the release of two hormones by the pituitary gland
FSH
- stimulates development of maturing ovarian follicle
- controls ovam production in female and sperm production in male
LH
- produced by pituitary gland
- stimulates ovaries to produce estrogen and progesterone
- triggers ovulation
- promotes development of corpus lutem
Estrogen
- maintenance of the female reproductive system
plays a role in
- puberty
- menstruation
- pregnancy
- menopause
Progesterone
- prepare lining of the uterus for fertilized egg
- support pregnancy
- suppress estrogen production after ovulation
78
What happens on day 14 of the menstrual cycle (feedback loop)?
LH levels will rapidly increase, causing ovulation, and making the follicle rupture.
79
What is the excretory system responsible for?
- Removing metabolic wastes. If they are not removed, homeostasis is disrupted and serious illness or death can result.
80
Function of the excretory system: 3 functions + 3 hormones
- Excretion of metabolic wastes, mainly nitrogenous (ammonia and urea/uric acid)
- Maintenance of water-salt balance- to regulate blood pressure
- Maintenance of acid-base balance to regulate blood pH
- Secretion of hormones such as
Calcitriol (active form of Vit D promotes Ca2+ absorption), Erythroprotein (produces red blood cells when 02 demands increase in the blood)
Renin (initiates production of aldosterone from adrenal cortex)
81
About the kidneys (2 major blood vessels and 3 regions)
- is bean shaped and reddish in color
- has 2 major blood vessels:
Renal: delivers blood to the kidney
Renal Vein: drains blood from kidney
- 3 regions in each kidney
Renal cortex: outer layer, encircles kidney.
Renal medulla: inner layer with cone shaped tissue masses.
Renal Pelvis: central space continous with the ureter
82
What does renal refer to?
Kidney
83
What is a nephron? (organized into 3 regions)
- embedded on the renal cortex, extends into renal medulla
- responsible for filtering blood
3 regions:
- a filter
- a tubule
- a collecting duct
84
What parts is the nephron made out of? (Bowman's Capsule, Long Tubule- 4 parts)
1. Bowman's Capsule
- cap formation that filters the blood
- within is a network of capillaries called a glomerulus
- walls of the glomerulus are impermeable to proteins + other large molecules + red blood cells
- water, small molecules, ions, and urea pass though and continue to Bowman's capsule. This material is called filtrate
2. Long tubule
- Bowman's capsule leads to a long tubule loop
- reabsorption of useful substances and secretion of substances into surrounding tissues happens
3 parts: the proximal tubule, the loop of Henle, the distal tubule
1 more part:
collecting duct, water conservation duct, reabsorbing water and some solutes returning to body
85
Urine formation in the Nephron (4 processes)
- Glomeralur formation: produces filtrate by moving blood plasma and solutes from blood to nephron
- Tubular reabsorption: removes useful substances from the filtrate and returns them to the blood for body use
- Tubular secretion: moves additional wastes from the blood into the filtrate
- Water reabsorption: collecting duct passively reabsorbs water from the filtrate by osmosis and returns it to the blood for use by body
86
What is the function of the loop of Henle?
- Absorbs most of the water and some salt
- Difference between descending limb and ascending limb
Descending limb:
- permeable to water and slightly permeable to ions
- located in the medulla where environemnt is very salty
- water diffuses from the filtrate to the capillaries by osmosis
- filtrate's concentration of sodium ions increases
Ascending limb:
- sodium ions are actively transported out of the filtrate and into the capillaries
- helps to replenish the medulla's salty environment and makes filtrate less concentrated
- two thirds of the sodium and water from the filtrate has been reabsorbed
87
What is the function of the Distal tubule
- Potassium and Sodium are secreted via active transport into the urine.
- Sodium and Cl are reabsorbed
- Water moves into urine through aquaporins
- Ionic pH balance is maintained
88
Collecting ducts
- Water moves out via the aquaporins
- There is no movement of ions
- Some urea leaves at the bottom of the collecting ducts
89
What homeostatic functions do the kidneys carry out? (3)
- maintaining the water-salt balance of the blood
- regulating blood pH
- secreting hormones
90
How do kidneys regulate the water-salt balance of the blood ? When the blood plasma is not as dilute. (osmotic pressure, osmoreceptors, ADH)
Osmotic pressure: the force generates as water moves by osmosis is called osmotic pressure- pressure affects the exchange of materials between cells and blood
Osmoreceptors: are nerve receptors that are sensitive to changes in osmotic pressure- located in the hypothalamus
- when blood plasma becomes concentrated, osmotic pressure increases
- osmoreceptors in the hypothalamus activate in the posterior pituitary gland to release ADH (anti-diuretic hormone)
- ADH travels through blood to kidneys, increases permeability of the distal tubule and collecting duct to allow more water reabsorption
- dilutes blood and lowers osmotic pressure
91
How do kidneys regulate the water-salt balance of the blood ? When the blood plasma is dilute. (osmotic pressure, osmoreceptors, ADH)
- osmotic pressure is low
- osmoreceptors in hypothalamus stop release of ADH
- distal tubule and collecting duct become less permeable to water and allow more water to be excreted in the urine
- concentrates the solutes in the blood and causes the osmotic pressure to increase
91
What is diabetes insipidus?
- ADH activity is insufficient so the person urinates excessively
-Leads the dehydration
91
Where is ADH release/occur, what affects does it have?
- happens in distal tubule and collecting duct
- ADH makes distal tubule + collecting duct more permeable to water, more water is reabsorbed from urine to blood.
92
Why are caffeine and alcohol called diuretics?
- They increase the volume of urine
- Inhibit ADH release which leads to urination and dehydration
93
How do kidneys regulate salt balance in the blood?
- When blood volume is low, the kidneys secrete an enzyme called renin to trigger the release of the hormone aldosterone from adrenal cortex
- Aldosterone makes potassium ions leave and brings Na ions in the distal tubule and collecting duct
- causes the reabsorption of chloride ions and water, causing blood volume and pressure in increase
94
What are the hormones produced by the Kidneys?
Erythropoietin: released when oxygen demands increase. Stimulates production of red blood cells in the bone marrow
Calcitriol: released when calcium levels decrease in the blood. Is the active form of vit D
95
What is the acid-base buffer system? What does it do?
Prevents the changes in pH by taking up excess hydrogen ions (H+) of excess hydroxide ions (OH-) that enter the blood.
