Module 5 Section 3: Animal Responses Flashcards
What does the cardiac muscle being myogenic mean
It does not require any external stimuli to initiate contraction, contraction is initiated by the muscle itself.
This allows the heart to beat at its own regular intervals
What systems regulate the length of the intervals between the beats
The rate of beating can be regulated by both the nervous system and endocrine system
What are the automatic control systems in the body
Nervous response
Controlled by electrical impulses travelling through nerve cells (called neurons)
Chemical response
Controlled by hormones travelling through the bloodstream
When may the heart rate increase
Exercise
When we activate fight or flight
How can the brain control the heart rate
There is a specific cardioregulatory centre region of the brain called the medulla which controls the heart rate
How do nerves and hormones play a part in fight or flight
Nerve impulses from sensory neurones arrive at the hypothalamus, activating both the hormonal system and the sympathetic nervous system.
The pituitary gland is stimulated to release a hormone called ACTH.
This causes the cortex of the adrenal gland to release steroidal hormones.
The sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region of the adrenal gland.
Effects of the sympathetic nervous system during fight or flight
Adrenaline is released
Heart rate increases - blood pumped round body faster
Muscles around bronchioles relax so breathing is deeper
Glycogen converted into glucose - more glucose available for muscles to respire
Smooth muscle in the arterioles supplying the skin and gut constrict
Smooth muscle in arterioles supplying heart, lungs and skeletal muscles dilate - means blood is diverted to these
Erector pili muscles in the skin contract - makes hair stand on end and animal looks bigger
What examples of hormones that increase heart rate
Noradrenaline
Adrenaline
Thyroxine
Nerves that change heart rate
Sympathetic nerves: increases heart rate
Parasympathetic nerves: decreases heart rate
How does the nervous system help to control heart rate
SAN generates electrical impulses that cause the cardiac muscles to contract
The rate at which the SAN fires (the heart rate) is unconsciously controlled by a part of the brain called the medulla
Why do animals alter their heart rate
It allows them to respond to internal stimuli
E.g. to prevent fainting due to low blood pressure or to make sure the heart rate is enough to supply the body with enough oxygen
How are the internal stimuli that control heart rate detected
Pressure receptors (baroreceptors) in the aorta and the vena cava
Stimulated by high and low blood pressure
Chemical receptors (chemoreceptors) in the aorta, the carotid artery (in the neck) and in the medulla
They monitor oxygen level in the blood, CO2 and pH (indicators of O2 level)
Pathway of impulses through nervous system to control heart rate
Sensory neurons take action potential from the receptors to the medulla
Medulla processes info and sends action potential to SAN along motor neurons
Pathway of change of heart rate when blood pressure is high
High blood pressure
Baroreceptors detect blood pressure
Impulses sent to medulla, which sends impulses along the vagus nerve
This secretes acetylcholine, which binds to receptors on the SAN
Cardiac muscles cause heart rate to slow down to reduce blood pressure back to normal
Pathway of change of heart rate when blood pressure is low
Baroreceptors detect low blood pressure
Impulses sent to medulla which sends impulses along accelerator nerve
This secretes noradrenaline which binds to receptors on SAN
Cardiac muscles cause heart rate to speed up to increase blood pressure back to normal
Pathway of change heart rate at high blood O2, low CO2 or high pH levels
Chemoreceptors detect chemical changes in the blood
Impulses are sent to medulla which sends impulses along the vagus nerve
This secretes acetylcholine which binds go receptors on SAN
Cardiac muscles cause heart rate to decrease to return O2, CO2 and pH levels back to normal
Pathway of change heart rate at low blood O2, high CO2 or low pH levels
Chemoreceptors detect chemical changes in the blood
Impulses are sent to medulla which sends impulses along the accelerator nerve
This secretes noradrenaline which binds to receptors on SAN
Cardiac muscles cause heart rate to increase to return O2, CO2 and pH levels back to normal
How do hormones increase heart rate and when can this happen
During fight or flight response
Adrenaline binds to specific receptors in the heart
Causes cardiac muscle to contract more frequently and with more force so heart rate increases and heart pumps more blood
How are the muscles used in the nervous system
The CNS (brain and spinal cord) receives sensory information and decides what kind of response is needed
If the response needed is movement, the CNS sends signals along neurones to tell skeletal muscles to contract
What is skeletal muscle
Skeletal muscle (also called striated, striped or voluntary muscle) is the type of muscle you use to move
e.g. the biceps and triceps move the lower arm
Structure of skeletal muscle
Skeletal muscle is made up of large bundles of long cells, called muscle fibres.
The cell membrane of muscle fibre cells is called the sarcolemma.
Areas of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm (a muscle cell’s cytoplasm).
These folds are called transverse (T) tubules
A network of internal membranes called the sarcoplasmic reticulum runs through the sarcoplasm
Function of sarcoplasmic reticulum
The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction
How are muscle fibres specialised
Muscle fibres have lots of mitochondria to provide the ATP that’s needed for muscle contraction.
They are multinucleate (contain many nuclei).
What do muscle fibres contain
Muscle fibres have lots of long, cylindrical organelles called myofibrils.
They’re made up of proteins called actin and myosin and are highly specialised for contraction