Organisms' response to their internal and external environments Flashcards
What is the point of organisms responding to changes in their environment?
Organisms increase their chance of survival.
What is the role of receptors?
Receptors detect stimuli. Receptors can be cells or they can be proteins on cell surface membranes.
What is the role of effectors?
Effectors are the cells that bring about a response to a stimulus, to produce an effect. Effectors include muscle cells and cells found in glands such as the pancreas.
How do receptors communicate with effectors?
They communicate via the nervous system or the endocrine system, or both.
What are cells in the nervous system called?
Neurones
What do sensory neurones do?
Sensory neurones are responsible for transmitting electrical impulses from receptors to the central nervous system- the brain and spinal cord.
What do motor neurones do?
Motor neurones transmit electrical impulses from the CNS to effectors.
What do relay neurones do?
Relay neurones transmit electrical impulses between sensory and motor neurones.
What are 2 other names for electrical impulses?
Nerve impulses
Action potentials
What is the name for the chemicals that take the information across a synapse to the next neurone?
Neurotransmitters
What is the 5 part reaction chain? (Starting with stimulus)
Stimulus > Receptors > CNS > Effectors > Response
What does the peripheral nervous system comprise of?
The neurones that connect the CNS to the rest of the body.
What are the two different systems of the peripheral nervous system?
The somatic nervous system
The autonomic nervous system
What is the role of the somatic nervous system?
The somatic nervous system controls conscious activities.
What is the role of the autonomic nervous system?
What are the two divisions of the autonomic nervous system and their roles?
The autonomic nervous system controls unconscious activities. The autonomic nervous system has two divisions with opposite effects on the body. The sympathetic nervous system gets the body ready for action- ‘fight or flight’. The parasympathetic nervous system calms the body down- ‘rest and digest’.
What is a reflex?
Where the body responds to a stimulus without making a conscious decision to respond.
What is the name of the pathway of neurones linking receptors to effectors in a reflex?
A reflex arc.
What does a simple reflex arc consist of?
A sensory neurone, relay neurone and motor neurone.
What possibility does the presence of a relay neurone in a reflex arc bring?
If there’s a relay neurone in the reflex arc, the reflex can be be overridden.
What three adjectives can be used to describe the nervous system?
Localised, short-lived, rapid
Why can the nervous response be considered localised?
When an electrical impulse reaches the end of a neurone, neurotransmitters are secreted directly onto target cells, so the response is localised.
Why can the nervous response be considered short-lived?
Neurotransmitters are quickly removed from the synapse once their job is done, keeping the response short-lived.
Why can the nervous response be considered rapid?
Electrical impulses are really fast, so the response is rapid, allowing animals to react fast to stimuli.
What are two other names for skeletal muscle and what is the function of this muscle type?
Striated muscle, voluntary muscle.
Skeletal muscle allows for movement of the body.
How are skeletal muscles attached to bones?
They are attached to bones by tendons.
What attaches bones to other bones?
Ligaments.
Pairs of skeletal muscles contract and relax to move bones at a _____. The bones of the skeleton are ______________, so they act as levers, giving the muscle something to pull against
joint
incompressible
What are muscles that work together to move a bone called?
Antagonistic pairs.
The contracting muscle is called the _______ and the relaxing muscle is called the antagonist.
agonist
Give an example of an antagonistic pair
Biceps and triceps.
What part do muscles play in the nervous system?
Muscles are effectors, stimulated to contract by neurones.
What are muscle fibres?
Muscle fibres are the long cells that make up muscle tissue.
What is the name for the cell membrane of muscle fibres?
The sarcolemma.
What are transverse tubules?
The folds where bits of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm.
What is the function of T tubules?
They help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.
What is the sarcoplasmic reticulum?
A network of internal membranes that run through the sarcoplasm.
What is the function of the sarcoplasmic reticulum?
The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction.
Why do muscle fibres have lots of mitochondria?
To provide the ATP that’s needed for muscle contraction.
Muscle fibres are multinucleate, what does this mean?
Each cell contains multiple nuclei.
Muscle fibres have long, cylindrical organelles called __________. They’re made up of proteins and are highly specialised for ___________.
myofibrils
contraction.
Myofibrils contain thick filaments and thin filaments. What are thick filaments made of and what are thin filaments made of?
Thick filaments are made of myosin protein.
Thin filaments are made of actin protein.
What do dark bands contain?
Thick myosin filaments and some overlapping thin actin filaments.
What are the dark bands called?
A bands
What do light bands contain?
Light bands only contain thin actin filaments.
What are the light bands called?
I bands.
What are the short units that make up a myofibril?
Sarcomeres.
The ends of each sarcomere are marked with….
…. a Z line.
In the middle of each sarcomere is an _-____
M-line
The M-line is the middle of the sarcomere.
Around the M-line is the _-____
H-zone
The H-zone contains only myosin filaments.
Describe the sliding filament theory of muscle contraction.
Myosin and actin filaments slide over one another to make the sarcomeres contract- the myosin filaments themselves don’t contract. The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract. Sarcomeres return to their original length as the muscle relaxes.
What happens within a sarcomere when contraction occurs?
The I-band gets shorter and the H-zone gets shorter, but the A-band stays the same length.
Myosin filaments have ________ _____ that are hinged, so they can move back and forth.
Globular heads.
Each myosin head has a binding for site for _____ and a binding site for ___.
Actin
ATP.
Actin filaments have binding sites for ______ _____, called actin-______ binding sites.
myosin heads
myosin
Name the protein found between actin filaments that helps myofilaments move past each other.
Tropomyosin.
What blocks actin-myosin binding sites in relaxed muscles?
Tropomyosin in the binding site. This prevents myofilaments from sliding past each other because the myosin heads can’t bind to the actin-myosin binding site on actin filaments.
What ions trigger muscle contraction?
Calcium ions.
How does a muscle contraction start?
When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma. Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum.
