Homeostasis and Nervous System Flashcards

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1
Q

Define homeostasis

A

a self-regulating process by which biological systems maintain stability while adjusting to changing external conditions

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2
Q

Define negative and positive feedback

A

NF- a response is required to oppose the stress/stimuli until a desired goal or ‘setpoint’ is maintained.
PF- a response reinforces an action in the same direction until a set goal is achieved

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3
Q

Outline the pathway for Negative Feedback

A

Variable -> Sensor-> Control-> Effector
Variable monitored by specialised receptors that detect change in local environment
Central unit (brain) that compares info from the sensor ( afferent feedback) to the ‘desired’ state ( setpoint)
Efferent pathway that is activated to correct any changes ( based on error determined at control) in the variable

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4
Q

Define both acid and base

A

acids: pH < 7, molecules that donate protons (H+), stronger acids more readily donate H++
Bases: pH 7-14, molecules that accept/ remove protons, stronger bases more readily remove H++

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5
Q

Define both Acidosis and Alkalosis

A

Acidosis- increase acidity builds up when bicarbonate ( a base) is lost
Alkalosis- body fluids have excess base ( alkali)

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6
Q

How does sodium bicarbonate act as a buffer system

A

H+ binds with bicarbonate
Forms carbonic acid
Buffer system- system that can resist change in fluid pH

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7
Q

what is the ‘normal’ acid- base pH level

A

Between 7.35 and 7.45

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8
Q

What are the branches of metabolism

A

Anabolism- combining simpler molecules to form complex molecular compounds, endergonic, consume more energy than they produce
Catabolism- breakdown of complex organic molecules into simpler components, exergonic- produce more energy than they consume

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9
Q

what are redox reactions

A

aid energy transfer within the body, via oxidation and reduction of molecules to transfer electrons.
Oxidation: loss of electrons
Reduction: gain of electrons

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10
Q

Outline ATP (Adenosine Triphosphate)

A

Global energy currency of cells, energy from chemicals is stored here, high- energy phosphate bond, splitting of ATP instant w/o 02, generates rapidly available energy
storage of ATP is finite & stores do not last long

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11
Q

Outline the ATP-PC energy system

A

ATP breakdown of ADP and single phosphate, phosphocreatine is then broken down by the enzyme creatine kinase into Creatine and phosphate, energy released from breakdown of PC allows ADP and Pi to re join- forming more ATP catalysed by ATPase.
Provides rapid source of energy, o2 not required

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12
Q

What occurs in glycolysis

A

Cytoplasm of the cell, anaerobic process
Phosphorylation- glucose (6C) + 2 phosphates = hexose bisphosphate
Lysis - destabilises the molecule causing it to split, 2 x triose phosphate (TP)
Phosphorylation- another phosphate group is added to each TP, forming 2 x triose bisphosphate
Dehydrogenation and formation of ATP- 2 x triose bisphosphate oxidised by the removal of hydrogen atoms (dehydrogenation) to form 2 pyruvate molecules.
NAD coenzymes accept the removed hydrogens
overall: 2 ATP, 2 reduced NAD

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13
Q

what occurs when energy demands is high

A

pyruvate act as a hydrogen acceptor taking the hydrogen from reduced NAD, catalysed by the enzyme lactate dehydrogenase.
Pyruvate is converted to lactate ( lactic acid) and NAD is regenerated.

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14
Q

outline points about lactate

A

lactate is produced at rest & under aerobic conditions
At rest, we have circulating blood lactate concentration of 0.5 - 2.0 mmol/L
Lactate is a pre- cursor for gluconeogenesis, cori cycle- transport to the liver for the production of glucose
Lactate facilitates continued glycolysis, buffers H+ accumulations and protects NAD+ concentration ( electron carrier)

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15
Q

Outline the process of the Krebs Cycle

A

takes place in the mitochondrial matrix, involves decarboxylation, dehydrogenation and substrate- level phosphorylation.
Acetyl CoA delivers acetyl group (2C) to the Krebs cycle, combine with 4 carbon oxaloacetate to form 6C citrate
Citrate molecule undergoes decarboxylation and dehydrogenation X2
2 x reduced NADs, 1 x reduced FAD , 1x ATP

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16
Q

outline the link reaction

A

Pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins
Pyruvate undergoes oxidative decarboxylation along with hydrogen
hydrogen atom is accepeted by NAD
Results two-carbon acetyl group bound by coenzyme

17
Q

Outline what occurs in the Electron Transport Chain

A

NADH & FADH are oxidised
Oxygen is final electron acceptor
Movements of electrons along the chain releases energy; H+ moves out
H+ creates a high potential energy. This initiates ATP synthase to phosphorylate ADP
Electron energy releases as it moves down the chain (resulting in H+ movement)
this creates an electrochemical gradient

18
Q

What are neurons

A

Specialised nerve cells, electrically excitable, communicate via travelling action potentials ( nerve impulses)

19
Q

What are Glial Cells

A

Highly abundant cells, help to protect neurons, do no generate or transfer action potentials, they can divide

20
Q

Define neurotransmitters

A

Chemical substances ( serotonin, dopamine, acetylcholine)
Facilitates synapses
Dopamine and Serotonin involved in many brain processes
Acetylcholine important for muscular contraction

21
Q

What are the features of a neuron

A

Axon- propagate impulses, sometimes coated in a myelin sheath
Axon terminals- project from terminal end of axons, neurotransmiters stored, site of synapse
Cell body- includes regular cell components
Dendrites- extended from cell body, receive information

22
Q

What are the types of Neurons

A

Sensory neurons ( Afferent, towards) - monitors internal/ external environments, once stimuli detected an action potential is generated
Motor neurons ( efferent, away from)- command, transfer impulses to effectors in the periphery ( muscles and glands)

23
Q

Outline the overview of the nervous system

A

CNS- brain and spinal cord, processes incoming sensory information, decides necessary action
PNS ( Peripheral Nervous System) : Autonomic Nervous System-> Sympathetic and Parasympathetic
Somatic

24
Q

Outline the features of the Peripheral Nervous System

A

Somatic Nervous System-> Sensory Neurons - provides information from the periphery, -> Motor Neurons: sends impulses from CNS to skeletal muscle only ‘voluntary’
Autonomic Nervous System- Sensory Neurons- provide information from organs, Motor Neurons -> sends impulses from CNS to smooth muscle, cardiac muscle & glands. ‘involuntary’

25
Q

Outline the features of the autonomic nervous system

A

sympathetic- increases HR, ‘fight or flight’
Parasympathetic- decreases HR, ‘rest and digest’

26
Q

Explain membrane potential

A

All excitable cells ( neurons, muscle cells) have a membrane potential
Potential difference (voltage) between charge and ion concentration inside and outside of the cell
Resting membrane is polarised, potential is negative ( more negative inside)
maintained by sodium- potassium pumps

27
Q

Outline the features of an action potential

A

Sodium ion movement alters the change
Depolarisation- Na+ gated channels open, increases Na+ entry to the cell
Repolarisation- Na+ gated channels close, K+ gated channels open

28
Q

Define synapses

A

Region of communication between cells- 2 neurons, neurons and effector cell ( muscle or gland)
Electrical Synapses- electrical impulse is passes to next cell, occurs in cardiac muscle cells
Chemical synapses- electrical impulse is converted into a chemical signal ( neurotransmitter)

29
Q

Outline what occurs in the neuromuscular junction

A

action potential stimulates releases of acetylcholine
Acetylcholine diffuses over synaptic cleft & binds to receptor
Causes Na+ to flow into the muscle cell= initiating an action potential across the muscle membrane

30
Q

Outline the features of the Neural Control of Movement

A

Neurons in the motor cortex= ‘Upper motor neurons ‘ communicate with downstream motor neurons
Neurons in the braistem & spinal cord= ‘lower motor neurons ‘
Axons innervate muscles to produce voluntary movement
Lower motor neurons innervate skeletal muscle to form motor units

31
Q

Define motor unit

A

Motor neuron & all innervted skeletal muscle fibres

32
Q

Eplain fibres in the context of motor units

A

Number of fibres is dependent on desired function
Muscle fibres for a single motor neuron are distributed througout the muscles
ALL muscle fibres will contract once a motor neuron is stimulated