The Nervous System Flashcards by Nicola Reed

What is meant by the term myogenic?

Muscle that contracts spontaneously without input from the nervous system

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Name the three types of muscle

Skeletal muscle, smooth muscle and cardiac muscle

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Striated muscle is made up of muscle________, each of which is made up of myofibrils.

Each myofibril is made up of myofilaments. The pattern of ________ myofilaments (made up of protein _______) and ________ myofilaments (made up of protein _______) gives the striation in the muscle

Fibres, thin, actin, thick, myosin

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What is a neurotransmitter?

A chemical messenger that diffuses across a synapse

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What is the cardiovascular centre?

A specific region of the medulla oblongata that receives sensory inputs about the levels of physical activity, blood CO2 concentration, and blood pressure.

It sends nerve impulses to the SAN in the heart to alter the frequency of excitation waves

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What is the medulla oblongata?

A region found at the base of the brain, that coordinates the unconscious function of the body, such as breathing rate and heart rate

The accelerator nerve and the vagus nerve run from the medulla oblongata to the heart

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What does myogenic mean?

Contraction if the muscle is generated from within the muscle itself

The term is used to describe the contraction of the heart, which is controlled by the action of SAN

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What is resting potential?

The potential difference or voltage across the neurone cell membrane while the neurone is at rest

It is about -60mV inside the cell compared with the outside

Other cells may also maintain a resting potential that might change under certain circumstances

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What are voltage gated channels?

Channels in the cell membrane that allow the passage of charged particles or ions

They have a mechanism called a gate which can open and close the channel

In these channels the gates respond to changes in the potential difference across the membrane

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What is the threshold potential?

A potential difference across the membrane of about -50mV

If the depolarisation of the membrane does not reach the threshold potential then no action potential is created

If the depolarisation reaches the threshold potential then an action potential is created

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What is an action potential?

A depolarisation of the cell membrane so that the inside of the cell membrane so that the inside is more positive than the outside, with a potential difference across the membrane of +40mV

This can be transmitted along the axon or dendron plasma membrane

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What are local currents?

The movements of ions along the neurone

The flow of ions is caused by an increase in concentration at one point, which causes diffusion away for, the region of higher concentration

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What are the first 4 stages of an action potential?

1 – The membrane starts in its resting state - polarised with the inside of the cell being -60mV compared to the outside

2 – Sodium ion channels open and some sodium ions diffuse into the cell

3 – The membrane depolarises - it becomes less negative with respect to the outside and reaches the threshold value of -50mV

4 – Voltage gated sodium ion channels open and many sodium ions flood in. As more sodium ions enter, the cell becomes positively charged inside compared with outside

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What are the last 4 stages of an action potential?

5 – The potential difference across the plasma membrane reaches +40mV. The inside of the cell is positive compared with the outside

6 – The sodium ion channels close and potassium channels open

7 – Potassium ions diffuse out of the cell, bringing the potential difference back to negative inside compared with the outside - repolarisation

8 – The potential difference overshoots slightly, making the cell hyper polarised. The original potential difference is restored so that the cell returns to its resting state

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Following stimulation, calcium ions binds to __________ on the actin filaments.

This cause another protein called __________ to change position and unblocked the binding sites on the actin filaments

Troponin

Tropomyosin

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The myosin heads attach to the binding sites, forming _________
bridges between the two filaments

Actomyosin

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_________ provides the energy for the cross-bridges to detach and reattach further along the actin filament

ATP

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Explain what is meant by a spinal reflex

A rapid and automatic response to a stimulus that does not involve though processes in the brain

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Name the three types of neurone involved in a spinal reflex, in order of their stimulation

Sensory neurone, relay neurone, motor neurone

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A hand is placed on a hot object and immediately withdrawn

For this reflex action, name:

a) the stimulus
b) the receptor
c) the coordinator
d) the effector

a) Touching the hot object
b) Heat receptors in the hand
c) Reflex arc in the spinal cord
d) Muscles involved in the withdrawal of the hand

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What is the autonomic nervous system?

The part of the nervous system that controls unconscious or involuntary activities, such as action of the heart or digestive system

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Describe the features of the sympathetic nervous system according to the following criteria:

a) neurotransmitter at synapses
b) effect on heart rate
c) effect on ventilation rate

a) Noradrenaline
b) Increased
c) Increased

Describe the features of the parasympathetic nervous system according to the following criteria:

a) neurotransmitter at the synapses
b) effect on heart rate
c) effect on ventilation rate

a) Acetylcholine
b) Decreased
c) Decreased

Name the two components of the central nervous system

The brain and spinal cord

State one function for: a) hypothalamus b) medulla oblongata

a) Homeostasis | b) Controlling heart and ventilation rates

Identify the parts of the brain that carry out the following functions: a) balance and posture b) voluntary activities, learning and memory

a) Cerebellum | b) Cerebrum

Distinguish between innate and learned behaviour

Innate behaviour is programmed at birth and is genetic in nature Learned behaviour is acquired during the lifetime of the organism through interaction with the environment

Distinguish between a taxis and a kinesis

A taxis is a directional movement in response to a stimulus — for example woodlice show negative phototaxis i.e. they move away from light A kinesis is a change in the rate of movement in response to a stimulus — for example sea anemones move their tentacles more when stimulated by chemicals emitted by potential prey

What is the term given to sequences of behaviour that control stereotyped responses such as courtship rituals?

Fixed action patterns

Describe what is meant by the term habituation

Learning not to respond to a neutral stimulus

What is meant by the term all-or-nothing?

All-or-nothing is a term used to describe the fact that action potentials in nerve cells are always identical in size

What is the refractory period of a neurone?

The time interval during which a nerve cell is incapable of responding to a stimulus

Name three factors that speed up the transmission if nerve impulses along axons

Diameter of the axon – impulses travel faster in larger axons because there is less electrical resistance Temperature – impulses go faster as temperature increases, up to 40C (above this, proteins begin to denature) Presence of a myelin sheath

What is a synapse?

The junction between two nerve cells

Name the two most common neurotransmitters found in synapses

Acetylcholine and noradrenaline

Vesicles containing neurotransmitter fuse with the ___________ and release their contents into the synaptic cleft Neurotransmitter diffuses across the cleft and attaches to _____________ on the post-synaptic membrane

Pre-synaptic membrane Receptor molecules

How does an inhibitory neurotransmitter work?

It makes the post-synaptic membrane hyperpolarised and therefore harder to excite

What is a neuromuscular junction!

The point at which a motor neurone connects with a muscle

Distinguish between temporal and spatial summation

Summation is the process that occurs in synapses due to the additive effect if a number of stimuli. A single stimulus may not be sufficient to trigger an action potential, usually because there is not enough neurotransmitter produced. In temporal summation, two or more impulses arriving at the synapse in a short period of time may generate an action potential – the effects of the impulse add up over time In spatial summation, an action potential may be triggered if several synapses act at the same time on the post-synaptic cell

What is neurone?

A cell specialised for the conduction of nerve impulses

What are the functions of the myelin sheath?

- To insulate and protect the neurone | - To speed up the conduction of nerve impulses

What are receptors?

Cells that are specialised to detect a particular stimulus

Outline how a stimulus might trigger a response in a sensory neurone

If the stimulus exceeds a minimum threshold value, the receptor is depolarised and an action is set up in a sensory neurone

Name four types of receptor found in humans

Baroreceptors (blood pressure) Chemoreceptors (blood pH) Photoreceptors (light) Mechanoreceptors (sound/pressure)

What are effectors?

Cells or organs that respond to a stimulus

State two types of effector found in animals

Muscles or gland

Distinguish between gluconeogenesis and glycogenolysis

Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources, such as lipid and protein. Glycogenolysis is the conversion of glycogen to glucose

Explain why insulin and glucagon affect mainly skeletal muscle cells and liver cells

Insulin and glucagon bind to protein receptors in the plasma membranes of skeletal muscle and liver cells. The protein receptors have a specific shape so that only these hormones will fit. Other body cells do not have these specific receptors

Name one hormone, other than insulin and glucagon, that can influence the concentration of plasma glucose

Adrenaline

Explain why the blood concentration of glucose rises during exercise, while that of insulin falls

During exercise, the skeletal muscles rapidly respire and therefore use a lot of glucose. Homeostatic mechanisms are required to increase the level of glucose in the blood Since glucagon stimulates a rise in blood glucose concentration, this hormone is secreted by the pancreas Insulin (which stimulates the concentration of blood glucose to fall) is not secreted

Explain how one molecule of glucagon can bring about the conversion of many molecules of glycogen to glucose

Many hormones operate on a cascade principle. When one molecule of glucagon binds to its receptor, it activates an enzyme which catalyses the breakdown of glycogen to glucose One enzyme molecule can catalyse the breakdown of many glycogen molecules The enzyme is said to have a high turnover rate

What is meant by the term resting potential?

In an unstimulated neurone, there is a high concentration of sodium ions outside the cell The inside is negative relative to the outside

Describe the changes that occur to the restoration of the resting potential when a neurone is stimulated

Depolarisation – Stimulation of the neurone causes sodium ions to enter the cell, making it positive relative to the outside. Repolarisation – Potassium ions then leave the cell, restoring the negative potential difference The true resting potential is then restored by sodium-potassium pumps, which actively transport potassium into the cell and sodium out of the cell