Nervous System Flashcards
CNS
This consists of the brain which processes information and is made up of interconnected neurons and the spinal cord which transmits information and is made up of a thick bundle of nerve tissue that carries information about the body to and from the brain.
PNS
This part consists of afferent (sensory) nerves that collect sensory information from the body and transmit it to the CNS and efferent (motor) nerves that carry commands from the CNS to the body.
From Stimulus to Response
A sharp pin that you touched is a stimulus. It’s a change in the environment detected by receptor cells in your fingers. This stimulus is converted into a nerve impulse. The nerve impulse then travels via nerve cells to the central nervous system where it gets processed and integrated by your your central nervous system by more nerve cells. The central nervous system formulates a response that is sent to the effectors which respond (in this case these would be muscles because you need to move your hand away from that really really sharp pointy pin). This all happens really really quickly, typically in milliseconds.
Myelin Sheath
The myelin sheath is a fatty substance that surrounds the axons entirely and it forms a kind of insulation on the axon almost like an insulated wire. This speeds up the impulses as they they travel along the axon.
SYNAPSES
Neurons use synapses to communicate. The axon releases a chemical called a neurotransmitter that’s picked up by the dendrite of another neuron, where it’s turned into an electrical signal.
Cerebrospinal fluid
The cerebrospinal fluid is found between the arachnoid mater and pia mater. It cushions the brain against shock (a shock absorber) and keeps the brain neutrally buoyant. It helps keep an even pressure and keeps the nervous tissue moist.
Meninges
Both the brain and the spinal cord are also surrounded by three membranes, collectively called the meninges.
Cerebrum
The largest part of the brain is the cerebrum and is divided into two halves called the left and right hemispheres. The left one, which controls the right side of your body, handles speech for most people. It also controls logic, maths calculations, and pulling facts from your memory. The right hemisphere, which controls your left side, is also in charge of music, recognising faces, and understanding your body’s position relative to what’s around you – what’s known as spatial awareness.
Cerebral cortex
the outermost layer of the cerebrum - this is where you’ll find your brain’s “gray matter,” which processes information.
Grooves
Many wrinkles and deep twisted grooves increase surface area
Nerves
A nerve is an enclosed, cable-like bundle of nerve fibres (axons), in the peripheral nervous system. A nerve provides a common pathway for the nerve impulses to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system.
A reflex arc:
The pathway along which an impulse is transmitted to bring about a response to a stimulus during a reflex action.
Significance of a reflex action:
the reflex action allows for a quick response, without thinking about it, to prevent damage to the body.
Significance of a synapse:
It ensures that the impulse moves in only one direction.
It prevents continuous stimulation of the neurons.
It ensures that the impulse is transmitted from the sensory neuron to the motor neuron.
The reflex action of a person touching a sharp pin:
- The stimulus is detected by receptors and converted into a nerve impulse.
- The nerve impulse is transmitted along the sensory neuron through the dorsal root to the spinal cord.
- The impulse is transmitted from the sensory neuron to an interneuron in the spinal cord.
- The impulse is transmitted from the interneuron to a motor neuron in the spinal cord.
- The impulse exits the spinal cord through the ventral root and is transmitted along the axon of the motor neuron to the effector organs (muscle; this causes the muscles in the limb to contract).
- The hand pulls away from the stimulus quickly.
