Final Flashcards
What is homeostatis
maintence of relatively constant conditions in the internal environment
what is negative feedback control in homeostatiss
- Negative because the response of the system is opposite in direction to the change that set in motion
Deviation away from its set point
describe steps negative feeback loop
- Sensors (input) > integrating centre (set of neural circuits in the brain or an endocrine gland) > compares regulated variable to set point > orchestrates response > output to the cells, tissues and organs
what is positive feedback control
- Same direction as the change that sets it in motion
e.g. of a tissu with gap juncitons?
cardiac
benefits of gap junctions
adjacent cells formed by connexins - connexon form channels that allow ions and small mocluels to pass direclty from one cell to another
juxtacrine communication?
direct contact btw cells - gap junctions
paracrine cellular communication?
short distance, immediate cellular environment, local coordiantin
autocrine cellular communication?
cell signals to self, self stimulation or self identitiy
endocrine cellular communication?
to distant sites, via hormones in the blood stream
what is an agonsit
ligands that binds to receptors and produces a biological response
e.g. of an agonist
E.G. morphine - opioid agonist used in the treatment of pain. Binds to mu opioid receptors in the spinal cord and brain and blocking pain signals from reaching consciousness. We have mu opioid receptors which prevent us from feeling pain under certain circumstances e.g. stress
what is an antagonist?
ligands that bind to receptors but do not produce a response - instead - they may compete with agonists for the receptor, decreasing the likelihood that the binding of agonist to receptor will occur and bring about a response
e.g. antagonist
E.g. naloxone - antagonist - binds to my opioid receptor 10x the strength of morphine - prevents morphine from binding there, reversing the effects of morphine
role of immune sstem
prevent infections and eradicate already estbalished infections
what does immunity refer to
bodys ability to recognise and eliminate microorgansims
what is innate immunity
intial protection agaisnt infection - blocks entry of microbes and eliminates those that do enter
what is adaptive immunity
specialised defence against infection
what are the phsyical and chemiCAL BARRIERS (immunity)
skin, respiratory system, stomach
how does the skin act as a barrier
sebaceous glands secrete sebum to inhibit bacterial growth
how does the respiratory system act as a barrier ( immunity)
mucus production which traps fogein particles that are inhaled
how does the stomach act as a barrier ( immunity)
HCI to kill ingested pathogens
what are the types of lymphoid cells
○ Natural killer cells - cells with abundant cytoplasmic granules, nonspecific defence against microorganisms
Lymphocytes - small cell with a large nucleus and very little cytoplasm, specific defence against a particular microorganism
cells in bone marrow
b cells
cells in thymus gland
t cells
what is ht ekey funciton of leukocytes
ability to migrate btw blood and tissue is key, important in detectign anitgens
e.g. of central lymphoid tissue
thymus galnd and bone marrow
e.g. peripheral lymphoid tissue
lymph nodes and spleen
what are the 4 types of nonspecific defence mechanism
○ Physical and chemical barriers
○ Inflammation
○ Interferons
Complement system
why are toll like receptors important
activate important signalling pathways that lead to activation of transcription factors
what is hte function of interferon regulatory factors
lead to transcription and secretion of type 1 interferon (IFN) which establishes an anti-viral state in the cell
whAt are inflammasomes
multi protien complexes that form in response to pathgoens - consists of a sensor and enzyme linked together by an adapter
function of RIG-like receptors
cystolic proteins that sense viral RNA,
funciton of cystolic DNA snesors (CDSs)
recognise DNA inthe cytoplasm, - DNA bidns to a DNA sensor called cGAS, which then activates a protein called STING, which eventually leads to the production of type 1 IFN
4 steps of phagocytosis
Macrophages have several receptors on the cell surface that can detect invading pathogens
1. Attachment: macrophages attaches to pathogen and recognises it as foreign
2. Internalisation: pathogen is engulfed into the cytoplasm into a vesicle called a phagosome
3. Degradation: phagosome fuses with lysosome (vesicle with digestive enzymes) and degrades pathogen
4. Exocytosis: debris is released from cell Important in limiting the initial spread of the pathogen
what are some fucntions of ISGs (interferon stimulated genes)
- Inhibit entry
- Inhibit viral replication
- Inhibit translation
- Inhibited release from cell
Enhance signalling pathways to produce more IFN
what is the complement system
A system consisting of approximately 30 proteins Upon activation there is a cascade of events (one protein activates another, which activates another etc.)
what is the classical pathway of the complement system
circulating antibodies to pathogen
what is the lectin pathway in the complement system
mannose-binding lectins bidnds to proteins on the surface of bacteria
what is the alternative pathway in compleemtn system
pathogen directly activate complement proteins
features of the adaptive immune system
memory,, speciifc, fiversity
what are the 2 major divisions of adaptive immune system
Humoral immunity
○ Mediated by B cells
- Cell-mediated immunity
○ Mediated by CD4+ helper T cells
○ and CD4+ cytotoxic T cells
what are some of the ways antibodies eliminate infections
- Neutralisation – antibodies bind to and block microbes from infecting a cell
- Agglutination – antibodies neutralise antigen and then clump together
Opsonisation – antibodies coat microbes (opsonisation) and promote their ingestion by phagocytes
- Agglutination – antibodies neutralise antigen and then clump together
compare autocrine and paracrine
autocrine - signal sent and received by presynaptic neuron
paracrine - signal from presynaptic neuron received on nearby postsynaptic neuron
what are ligand gated channels
ion channels that open or close in response to the binding of a chemical to a receptor or to the channel
what is a trophic hormone
a hormone that controls the secretion of other hormones
what is a stimulating hormone
increases the secretion of another hormone
what is an inhibiting hormone
decreases the secretion of another hormone
what is retrograde transport
from axon terminal to cell body
what is anterograde transport
from cell body to axon terminals
what are bipolar neurons
sensory neurons with 2 proections - axon and dendrite - funciton: olfaction and vision
what are pseudounipolar neurons
xon and dendrite projections appear as a single process that enstends in two directions BUT the dendrite is modified to function much like an axon
fucniton of glial cells
- Function: providing structural integrity to the nervous system and chemical and anatomical support that permits neurons to carry out their functions , supply nutrienrs, electrical insulation
function of astrocytes
- Transport nutrient from blood vessels to neurons
- Remove neurotransmitters (glutamate and GABA) released by neurons during synpatic transmission
- Regulate extracellular potassium concentrations
funciton of oligodendrocytes and schwann cells
- To form an insulating layer of myelin around the axons of neurons
- Myelin is: a greatly extended and modified portion of the cell membrane that wraps around the axon in spiral fashion
- Rich in lipid –> provides effective electrical insulation of the axon
- Oligodendrocytes - CNS -
Schwann cells - PNS
function of microglia
- Immune effect cells of the CNS
- Phagocytose cell debris following injury
- Brain development ad homeostasis
- Promote regrowth and remapping of damaged neural circuitry
Involved in neuronal and synaptic plasticity
how many Na+/K+ in and out in the ATPase pump
- 3 Na+ transported out of the cell
2 K+ transported into the cell
what hapens when Na+ flows into a cell
cell inside becomesmore positive
what is the current if K+ ions are flowing out of the cel
outward K+ current
what is the current if Na+ ions are flowing into the cell
inward Na+ current
if ion inside is greater than the ion outside how will ions diffuse?
ions will diffuse out
what is the eletrical driving force
acting on charged particles and has hte potential to cause those particles to move
what are cations
attracted by the negative change inside the cell, have an inward directed electrical driving force
what are anions
repelled by the negative membrane potential and have an outward directed electrical driving force
what does the electrochemical driving force determine?
- It determines the direction in which the ions move if they are allowed to cross the membrane spontaneously.
What occurs during ventricular filling?
Blood enters the relaxed atria and passes through the AV valves into the ventricles under its own pressure.
Why does venous return occur?
Because the pressure in the veins is greater than that in the atria.
What happens at the end of diastole?
the atria contract, driving more blood into the ventricles.
What is isovolumetric contraction?
A phase where all valves are closed, and no blood flows into or out of the ventricles despite contraction.
When does isovolumetric contraction end
When ventricular pressure is sufficient to force open the semilunar valves.
What occurs during ventricular ejection?
Blood is ejected into the aorta and pulmonary arteries, causing ventricular volume to fall.
What marks the beginning of diastole?
The closure of the semilunar valves after ventricular pressure falls below aortic pressure.
Describe isovolumetric relaxation.
: All valves are closed, and the volume of blood in the ventricles remains constant as they relax.
What initiates heart contractions?
Pacemaker cells that spontaneously generate action potentials, primarily in the SA and AV nodes.
What is the role of conduction fibers in the heart?
They quickly conduct action potentials generated by pacemaker cells through the myocardium.
What allows efficient transmission of action potentials in cardiac muscle?
Gap junctions that connect all cardiac muscle cells.
How do the left and right ventricles differ?
The left ventricle has a thicker wall to pump blood at higher pressure throughout the body.
What do blood vessels do in the cardiovascular system?
hey regulate blood pressure and distribute blood to various parts of the body.
What is the epimysium?
Connective tissue that surrounds the body of the muscle.
What does the endomysium do?
It is a thin sheath of connective tissue that encases muscle fibers.
What are myofibrils?
: Structures that contain the fibers’ contractile machinery, composed of thick and thin filaments.
What is a sarcomere?
The fundamental unit of myofibrils that repeats over and over, bordered by Z lines.
What are thick and thin filaments made of?
Thick filaments are made of myosin, and thin filaments are made of actin and regulatory proteins (tropomyosin and troponin).
What is the role of tropomyosin in muscle contraction?
It blocks myosin-binding sites on actin when muscles are at rest.
What is the function of troponin?
: It binds to actin, tropomyosin, and calcium, facilitating muscle contraction by exposing myosin-binding sites on actin.
Describe the structure of myosin
Myosin molecules are dimers with long tails and protruding heads; the heads bridge the gap between thick and thin filaments