-Module 5.1.5 Animal Flashcards
What are the two main bodies of the nervous system?
CNS and peripheral
What is the function of the CNS?
To receive and process information and coordinate the body’s response
What is the function of the peripheral nervous system?
Neurones that carry action potentials to and from the CNS.
What are the two components of the CNS?
Brain, spinal chord`
What are the two neurones involved in the peripheral nervous system?
Motor and sensory.
What is the function of motor neurones in the PNS?
Carry action potentials from the CNS to effectors (muscles and glands)
What is the function of sensory neurones in the PNS?
Carry action potentials from receptors to the CNS.
What are the two components of the motor neurone system?
Autonomic and somatic.
What is the role of the autonomic nervous system?
Controls the involuntary activities of glands, smooth muscle and cardiac muscle. Works constantly under subconscious control. Eg heartbeat and food digestion
What is the role of the somatic nervous system?
Controls the voluntary activities of body muscles. It is under conscious control eg deciding to move your arm.
What two nervous systems are in the autonomic nervous system?
Sympathetic and parasympathetic.
What involves the sympathetic nervous system?
If the outcome is increased activity then it involves the sympathetic nervous system. eg heart rate increase.
What involves the parasympathetic nervous system?
If the outcome is a decrease in activity, a decrease in heart rate and breathing rate.
What nervous reactions are processed by the brain?
All except reflex actions.
Why is having one central control centre in the brain advantageous?
It provides a more rapid response.
What is most of the brain made up of?
Relay neurones, most of which are non-myelinated so the tissue looks grey.
What are the different parts of the brain?
Skull, cerebrum, cerebellum, medulla oblongata, spinal chord, hypothalamus, pituitary gland.
What is the function of the cerebrum and where is it?
It is the outer layer of the brain and controls voluntary actions such as learning, memory, personality, language and conscious thought.
What is the function of the cerebellum and where is it?
It is the part of the brain at the back and below the cerebrum. It controls unconscious functions such as posture, balance and non-voluntary movements.
What is the medulla’s function and where is it?
It is found below the brain in front of the cerebellum. It is used in autonomic control such as heart rate and breathing rate.
What is the function of the hypothalamus and where is it found?
It is found below the main body of the brain just above the pituitary gland. It is the regulatory centre for temperature and water balance.
What is the function of the pituitary gland and where is it found?
Stores and releases hormones that regulate many body functions (AHD)
What is the structure of the cerebrum?
It splits into left and right hemisphere. The left side of the brain controls the effectors on the right side of the body and vice-versa.
The two hemispheres are connected by the corpus collosum.
The outer layer is thin and is highly folded and is called the cerebral cortex.
It interprets information that it receives with respect to that stored from previous experiences.
Action potentials are sent along motor neurones to produce an appropriate response.
What are the functions of the cerebrum?
Conscious thought and actions,
Emotional responses,
Intelligence, reasoning, judgement and decision making
Factual memory
Sensory areas
Association areas - compare sensory inputs with previous experience
Motor areas - send action potentials to effectors
What is the function of the cerebellum?
It is involved with the control of muscular movement, body posture and balance, doesn’t initiate movement but coordinates it.
Coordinates the fine control of movements which are learned and improve with practice until they often involve much unconscious control,
What can happen if the cerebellum is damaged?
A person suffers from jerky, uncoordinated movement.
What are the cerebrum and cerebellum connected by?
The pons.
What part of the body does the cerebellum receive information from?
Retina.
Balance organs in the inner ear.
Spindly fibres in muscles - tone of muscles and tendons.
What does the hypothalamus control and contain?
Sensory receptors and controls homeostatic mechanisms.
What two lobes does the pituitary gland consist of and what do they do?
Posterior lobe - linked to the hypothalamus by specialised neurosecretory cells (release of ADH)
Anterior lobe - produces it’s own hormones which are released in response to factors produced by the hypothalamus.
What do the two centres of the hypothalamus do?
One is for the parasympathetic and one for the sympathetic nervous system.
What do the functions of the hypothalamus include?
Controlling complex patterns of behaviours such as feeding, sleeping and aggression.
What does the medulla do?
It controls the non-skeletal muscles by sending out action potentials through the autonomic nervous system.
What are examples of the different centres of the hypothalamus?
Cardiac centre - regulates heart rate.
Vasomotor centre - regulates circulation and blood pressure.
Respiratory centre - regulates the rate and depth of breathing.
What is a reflex action?
It is where the body responds to a stimulus without making a conscious decision to respond. This is because pathways of communication doesn’t involve the conscious parts of the brain. Reflex actions are protected and help organisms avoid damage.
What are the main features of a reflex action?
Rapid
Automatic
Involuntary
Sub-conscious
What is the path of communication in a reflex action?
Stimulus -> receptor -> sensory neurone -> CNS -> motor neurone -> effector -> response.
How can the blinking reflex (or any with a relay neurone) be overridden?
When a relay neurone is part of the pathway, the reflex arc can be consciously overridden by inhibitory signals. This allows the person to touch their eye.
What is the purpose of the knee-jerk reflex?
Used to help maintain posture and balance by causing the lower leg to straighten rapidly. Abscence may indicate an issue with nervous system.
Does the knee jerk reflex have a relay neurone?
No
Why is an inhibitory relay neurone needed for the knee jerk reflex to occur?
The muscles in the leg are found in antagonistic pairs. During the knee-jerk reflex, an inhibitory electrical impulse is sent, causing it to relax. This is done via a relay neurone.
How do we manage to bend our knees when running and walking?
As action potentials are sent to the hamstrings stimulating them to contract. inhibitory action potentials are sent to the synapse in the reflex arc to prevent the reflex contraction of the quadriceps muscle.
What receptors are involved in detecting threat? What part of the brain detects this sensory input?
External receptors, eyes, ears and nose.
Internal receptors, pain and blood pressure.
The cerebrum detects this sensory input.
How does the coordination of the flight or fight system take place?
The cerebrum recognises a threat and stimulates the hypothalamus.
The hypothalamus increases activity in the sympathetic nervous system and the endocrine system.
Hypothalamus releases 2 hormones.
1- Corticotropin-releasing hormone (CRH) which causes the release of adrenocorticotropic hormones (ACTH) from the pituitary gland.
2- Thyrotropin-releasing hormone (TRH) which causes the release of thyroid-stimulating hormone (TSH).
ACTH causes the adrenal cortex to release glucocorticoids (eg cortisol) which regulate the metabolism of carbohydrates (eg increasing gluconeogenesis)
The adrenal cortex also releases mineralocorticoids such as aldosterone which increases blood volume and blood pressure by increasing the uptake of sodium ions and water by the kidneys.
TSH stimulates the thyroid gland to release more thyroxine which increases the basal metabolic rate and makes cells more sensitive to adrenaline.
The sympathetic nervous system activates the release of adrenaline from the adrenal medulla. Together the SNS and adrenaline cause a rapid response.
What happens when fight or flight kicks in?
Heart rate increases and heart contraction force increases.
Bronchiole muscles contract causing airways to widen and breathing to deepen.
Intercostal muscles and diaphragm contract faster to increase rate and depth of breathing.
Glycogenolysis - release of glucose into bloodstream as respiration rate increases.
Vessels supplying heart and muscles dilate so more blood brings oxygen and glucose to these tissues. Vessels supplying digestive system and skin constrict.
Erector pili muscles in skin contract - hair stands on end - animal looks bigger.
How is the cardiac cycle controlled by the brain?
Heart rate is involuntary and controlled by the autonomic nervous system. The medulla oblongata in the brain controls the heart rate. The cardiovascular centre in the medulla oblongata linked to the sinoatrial node (SAN) in the heart by motor neurones.
How is heart rate increased by the nervous system?
Action potentials pass along a sympathetic nerve causing the release of the neurotransmitter noradrenaline at the SAN.
How is heart rate decreased by the nervous system?
Action potentials pass along a parasympathetic nerve causing the release of the neurotransmitter acetylcholine.
What are baroreceptors?
They are pressure/stretch receptors that detect changes in blood pressure, located in the aorta, vena cava and carotid arteries.
Why does heart rate need to increase when blood pressure drops?
To prevent fainting.
What are chemoreceptors?
Chemical receptors that monitor and detect changes in oxygen and carbon dioxide concentration. Sensitive to changes in the pH levels in the blood. Located in the aorta, carotid artery and medulla.
Where are nerve impulses from chemoreceptors and baroreceptors sent to and what happens from there?
The cardiovascular centre in the medulla oblongata which processes the information and sends impulses to the SAN along motor neurones.
What happens to the pH of the blood when carbon dioxide increases?
Carbon dioxide reacts with water to form carbonic acid, thus lowering the pH.
How is most carbon dioxide transported in the blood?
As hydrogencarbonate ions. The carbonic acid dissociates to release hydrogen ions.
What is the effect of the increase of hydrogen ions and carbonic acid on red blood cells?
The H+ affects the pH of the cytoplasm in the red blood cells.
This alters the shape of the haemoglobin, reducing it’s affinity for oxygen.
The H+ can react with haemoglobin to form haemoglobinic acid and the HCO3- can react with haemoglobin to form carbaminohaemoglobin.
Haemoglobinic acid and carbaminohaemoglobin are unable to combine with oxygen as normal.
How is heart rate controlled in response to high blood pressure?
Baroreceptors detect high blood pressure and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along the parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN. This causes the heart rate to slow down and blood pressure to return to normal.
How is heart rate controlled in response to low blood pressure?
Baroreceptors detect low blood pressure and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along sympathetic neurones. These secrete noradrenaline which binds to receptors on the SAN. This causes heart rate to increase which increases blood pressure back to normal.
How is heart rate controlled in response to high oxygen concentration/low carbon dioxide concentration/high blood pH levels in the blood?
Chemoreceptors detect the chemical changes and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along the parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN and causes heart rate to decrease to return oxygen, carbon dioxide and pH levels to normal.
How is low oxygen concentration/low carbon dioxide concentration/high blood pH levels in the blood?
Detected by chemoreceptors which send impulses along sensory neurones to the cardiovascular centre, which send impulses along the sympathetic neurones. These secrete noradrenaline which binds to receptors on the SAN. This causes heart rate to increase to return oxygen, carbon dioxide and pH levels to normal.
How is heart rate influenced by hormones?
In times of stress adrenaline and noradrenaline are released. These hormones affect the pacemaker cells of the heart and speed up heart rate by increasing frequency of impulses produced by the SAN.
Why does moving limbs cause an increase in heart rate and how does it happen?
Stretch receptors in the muscles detect movement of limbs. These send action potentials to the cardiovascular centre in the medulla oblongata leading to an increase in the heart rate.
Where is the cardiovascular centre found?
The medulla oblongata.
What are the 3 different types of muscle?
Smooth muscle (involuntary), striated/ skeletal muscle (voluntary) and cardiac muscle.
Where is involuntary/smooth muscle found?
In the walls of hollow organs, eg bladder and stomach.
Walls of blood vessels.
Digestive tract, where peristalsis moves food along the gut.
What part of the nervous system is smooth muscle under control of?
Autonomic nervous system.
What is smooth muscle like in terms of speed of contraction and fatigue?
Both slow.
Where is cardiac muscle found?
ONLY IN HEART.
What does it mean that cardiac muscle is myogenic?
Contracts without the need of a nervous stimulus which causes the heart to beat in a regular rhythm.
How does cardiac muscle produce simultaneous contraction?
The cells are interconnected
Are striations seen in cardiac muscle?
Yes but fainter than skeletal muscle.
What are the fibres in cardiac muscle like?
They are branched and uninucleated.
How are cardiac muscle cells joined?
Joined by interclated discs which allow free movement of ions between cells so that action potentials can pass quickly along and between cardiac muscle fibres.
What is cardiac muscle like in terms of contraction and fatigue?
It contracts spontaneously and doesn’t fatigue.
What are skeletal muscles involved in?
Voluntary movement, eg biceps and triceps,
What does the name skeletal/striated muscle come from?
It’s stripy or striated appearance under the microscope due to the arrangement of actin and myosin.
What is skeletal/striated muscle like in terms of speed of contraction and fatigue?
Contracts rapidly but also fatigues rapidly.
What type of nervous system is skeletal muscle under the control of?
Somatic
How are muscles attached to bones?
Tendons
What is a muscle bundle?
Muscles are made up of bundles which consist of muscle fibres. Each bundle is surrounded by connective tissue and holding blood capillaries and nerves.
What is a muscle fibre?
Muscle cells fuse together during embryonic development to form a muscle fibre. This causes long, strong multinucleated cells to form. Without fusion the cells would be weak.
What are muscle fibres made up of?
Each muscle fibre is made up of many myofibrils. They are found within the cytoplasm (sarcoplasm) of the muscle cells. They have characteristic dark and light pattern called striations.
What is a sarcomere?
It is the smallest contractile unit of a muscle. They are arranged end to end along the length of the myofibril.
What is a sarcomere formed out of?
Thousands of protein filaments. These proteins can slide togther, shortening the sarcomere. This is how muscles contract.
What is the sarcolemma?
It is the plasma membrane that encloses the muscle cells. Part of the sarcolemma folds inwards and this is called the transverse or T-tubules.
What are T tubules and what is their role?
They are parts of the sarcolemma that fold inwards, their role is to spread electrical impulses throughout the sarcoplasm so that the whole fibre receives the impulse to contract simultaneously.
Why are there many mitochondria in the muscles?
They provide the ATP required for muscle contraction.
What is the sarcoplasmic reticulum?
It is a modified endoplasmic reticulum in muscle fibres that extends through the muscle fibre and supplies the calcium ions needed for muscle contraction.
What are myofibrils?
Bundles of protein filaments.
How do myofibrils look and why?
They have a striped appearance due to alternating light and dark bands from the specific positions of the actin and myosin.
Why do myofibrils run in parallel?
To provide the maximum force when they all contract together.
What two types of protein myofilaments are myofibrils made up of?
Actin - thinner filament consisting of two strands twisted around each other.
Myosin - thicker filament consisting of long rod-shaped fibres with bulbous heads.
What is the structure of the sarcomere?
Light bands appear light as this is where actin and myosin do not overlap. AKA I bands.
Dark bands appear dark because of the presence of thick myosin filaments. The edges are especially dark as this is where myosin is overlapped with actin. They are known as A-bands.
Z-line marks the boundary of the sarcomere (found in the centre of the light band).
H-zone, a lighter coloured region in the centre of each dark band where only myosin is found.
What is the H-band?
Only thick myosin filaments is present. It is lightly coloured in the centre of each dark band.
What is the I-band?
Only thin actin filaments are present. They appear light as this is where actin and myosin don’t overlap.
What is the A-band?
Contains areas where only myosin filaments are present and areas where myosin and actin filaments overlap. Dark because of the presence of thick myosin filaments.
What is the M-line?
Where there is attachment for myosin filaments.
What is the Z line?
Attachment for actin filaments.
What is the sarcomere?
The section of myofibril between two Z-lines.
What is the point of the neuromuscular junction?
For a muscle to contract, an action potential must arrive at a neuromuscular junction - the point where a motor neurone and skeletal muscle fibre meet.
What is the muscle fibre connected to a single motor neurone called?
Motor unit.
How is it ensured that all muscle fibres contract simultaneously?
There are many neuromuscular junctions along the length of the muscle.
What is the difference in neuromuscular activity in a small force and large force?
Small forces require only a few motor units to be stimulated.
Large forces require many motor units to be stimulated.
How is the area that impulses are received increased?
The muscle fibre surrounds the end of the neurone to increase the area that impulses are received over.
What happens when an action potential arrives at the motor neurone? How is the impulse transmitted to the sarcoplasmic reticulum?
Causes Ca2+ channels to open and Ca2+ ions flood into the cell.
The Ca2+ stimulate the vesicles containing acetylcholine to move towards the presynaptic membrane and fuse with it.
Acetylcholine released by exocytosis and diffuses across the synaptic cleft and binds to the receptors on the postsynaptic membrane (sarcolemma).
This results in Na+ channels opening and Na+ flooding into the muscle cell.
The sarcolemma depolarises.
If the threshold point is reached an action potential is generated.
The electrical impulse travels into T-tubules.
Action potential moves towards sarcoplasmic reticulum.
This releases Ca2+ into the cytoplasm.
How is acetlycholine broken down and into what?
Broken down by acetylcholinesterase into choline and ethanoic acid.
Why is acetylcholine being broken down important?
It prevents the muscle from being overstimulated.
Chlorine and ethanoic acid diffuse back into the neurone and are recombined into acetylcholine.
Process requires energy from mitochondria.
What is muscle contraction caused by?
Contraction of the sarcomere.
What happens to the light band, Z lines and H zone when a sarcomere contracts?
Light band narrows.
Z line moves closer together to shorten the sarcomere.
The H zone narrows.
Why does the dark band stay the same width during contraction?
Myosin filaments themselves do not shorten. Instead, they now overlap the actin filaments by a greater amount.
What is the structure of myosin?
Myosin filaments have globular heads that are hinged allowing them to move backwards and forwards.
On each head is a binding site for ATP and actin.
The tails of hundreds of myosin molecules align to form the filament.
The head can act as an ATPase enzyme, hydrolysing ATP to ADP + Pi.
What does a single myosin molecule consist of?
Two intertwined polypeptide chains (tail/filament)
What is the structure of actin in a relaxed state?
An actin filament is made up of two chains of actin monomers joined together.
Actin filaments have binding sites for myosin heads called actin-myosin binding sites - these are often blocked by the prescence of another protein called tropomyosin which is held in place by troponin.
Troponin is bound to tropomyosin.
What does tropomyosin do in a relaxed state?
It blocks the binding sites on the actin filament, preventing the myosin heads from binding to the actin.
What does the release of Ca2+ do to the tropomyosin?
At high concentrations of Ca2+ they bind to troponin on the actin filament. This causes tropomyosin to change shape, exposing the binding sites.
The activated myosin heads can now bind to the actin molecules to form cross bridges which produces tension in the muscle.
Binding to the actin causes the myosin head to change shape. This causes the entire actin filament to be pulled along the myosin.
ADP can now be released from the myosin head.
ATP can then bind to the myosin head.
Broken down to ADP and Pi to release energy.
Energy allows the myosin head to release the actin and return to it’s original state.
The cycle can now repeat, dragging the actin filament further along the myosin.
The sarcomere will continue to contract if there is a ready supply of ATP.
How does the tropomyosin return to it’s original state when movement is finished?
Calcium is actively removed from the sarcoplasm when the muscle is no longer stimulated by a nerve.
This causes tropomyosin to return to its original shape.
What do antagonistic muscles do to the sarcomere?
They pull the fibres apart as there are no forces holding the fibres together.
What are the 3 main ways that ATP can be generated?
Aerobic respiration.
Anaerobic respiration.
ATP-creatine phosphate system.
How is ATP produced by aerobic respiration?
Most of the ATP is generated via oxidative phosphorylation in a cell’s mitochondria. Oxygen is required therefore it’s good for long periods of low intensity exercise.
How is ATP produced by anaerobic respiration?
ATP is made rapidly during glycolysis. The end-product is pyruvate which is converted into lactate, by lactate fermentation. Lactate can build up in the muscles causing fatigue. Muscles can no longer contract as forcefully as before. Good for short periods of hard exercise.
How does the ATP-creatine phosphate system produce ATP?
ATP is made by phosphorylating ADP - adding a phosphate group taken from creatine phosphate (CP). CP is stored inside cells and the ATP-CP system can generate ATP very quickly. CP runs out after a few seconds, so is used during short bursts of vigorous exercise eg a tennis serve.
What is the equation for the ATP-creatine phosphate system?
ATP + CP –> ATP + C
How does rigor mortis occur?
After death oxygen rapidly depletes. Ca2+ binds to troponin and with no ATP available, the myosin heads remain bound in a contracted format.
