Homeostasis Flashcards
What is the nervous system responsible for?
receiving information about the external and internal environment, processing the information and generating a response
What are the 3 parts of the nervous system?
the brain, spinal cord and nerves
What are the 3 principle functions of the nervous sysetm?
sensory input, integration and motor output
What is sensory input?
receiving information about changes in the environment from sensory neurons
What is integration?
interpreting the information in the brain or spinal cord by interneurons
What is motor output?
coordinating a response from muscles or glands by motor neurons
What are the 2 major divisions of the nervous system?
The central nervous system and the peripheral nervous system
What does the CNS consist of?
the brain and spinal cord
What does the CNS do?
takes in information from sensory receptors, processes it, coordinates an appropriate response by effectors
What does the CNS contain?
mainly interneurons
What is the PNS made of?
sensory organs, effectors and nerves
What does the PNS do?
relays signals to the CNS from sensory receptors, motor nerves relay signals from the CNS to effectors
What does the PNS consist of?
sensory and motor neurons
What are the 2 types of nervous system cells?
neurons and glial cells
What do neurons do and how many are there?
receive and transmit nerve impulses throughout the nervous system, 3 kinds
What do glial cells do and how many types are there?
they provide support for neurons and there are 5 main types
What is a neuron?
the structural and functional unit of the nervous system
How many types of structural types of neurons are there and what are they?
3, multipolar neurons, bipolar neurons and pseudounipolar neurons
What are multipolar neurons?
a neuron with many dendrites, one axon and a cell body near the dendrites
What are bipolar neurons?
a neuron with one dendrite, one axon and a cell body in the middle
What is a pseudounipolar neuron?
a neuron with a cell body with 1 extension split into 2 axons with dendrites at the ends
What are the functional neurons and how many are there?
3, sensory neurons, interneurons and motor neurons
What do sensory neurons do?
they transmit signals from sensory receptors to the CNS
What do interneurons do?
they transmit signals between sensory and motor neurons
What do motor neurons do?
they transmit signals from the CNS to muscles and glands
What do interneurons allow?
they allow the nervous system to integrate information and coordinate a response
What is a reflex?
a rapid, automatic response that bypasses the brain
What is a nerve?
a cable-like bundle of multiple axons wrapped in layers of connective tissue and fat
How many types of nerves are there and what are they?
3 types, sensory nerves, motor nerves and mixed nerves
What do sensory nerves do?
they transmit nerve impulses from sense organs to the CNS
What do motor nerves do?
they transmit nerve impulses from the CNS to muscles or glands
What do mixed nerves do?
they transmit nerve impulses in both directions
What are Schwann cells and what do they do?
they wrap around the PNS neurons to form sheaths made of myelin and they speed up transmission
How does a nerve impulse work?
begins at the cell body, travels along the axon, and passes to another neuron or effector at the axon terminal
What is an action potential?
an electrochemical event that is created by a sudden change in the concentration of ions on opposite sides of a neurons cell membrane
What are the steps of the action potential?
resting potential, depolarization, repolarization, hyperpolarization
What is happening to the neuron during resting potential?
the neuron is not firing, action potential is not occurring, a sodium-potassium pump actively pumps 3Na+ ions out of the cell and 2K+ ions in the cell to keep the cell balanced
What is the charges on either side of the cell during resting potential?
positively charged outside and negatively charged inside
What is the voltage level during resting potential?
-70mV
What happens at the threshold?
When a stimulus is triggered, Na+ channels open allowing the ions to rush into the cell, causing a small depolarization
What does the voltage rise to during the threshold?
-55mV
What happens during depolarization?
Once the -55mV is hit, more Na+ gated channels open allowing more ions to rush into the cell causing an even more depolarization
What is the voltage during depolarization?
+35mV
What happens during repolarization?
when the voltage hits +35mV, the cell begins to repolarize and Na+ gated channels close and K+ gated channels open and potassium ions rapidly diffuse out of the cell which decreases the voltage
What is the voltage during repolarization?
-70mV
What happens during hyperpolarization?
The K+ gated channels stay open for slightly longer than needed to bring the membrane back to the resting potential
What is the voltage during hyperpolarization?
-75mV
What happens after hyperpolarization?
the sodium potassium pumps regulate the voltage back to -70mV and the neuron goes back to being in the resting potential phase
What is the refractory period?
the time after an action potential where a neuron cannot fire again
What is the absolute refractory period?
a neuron cannot have another action potential due to inactive Na+ channels
What is a relative refractory period?
a neuron can have a action potential with larger stimulus due to K+ channels still being open
What is the all or none rule?
action potentials occur fully or not at all action potentials don’t change sizes
What are synaptic bulbs?
knob like tips are the end of axon terminals on the neuron
What is the synapse?
the junction between the synaptic bulb of one neuron and another neuron or an effector
What is the synaptic cleft?
a tiny gap where a nerve signal is transmitted
What are chemical messengers?
neurotransmitters
What is the spinal cord?
a cord of nerve tissue that passes down from the brain through a bony column formed by the vertebrae
What is the spinal cord composed of?
interneurons and motor neurons
What are the 2 functions of the spinal cord?
connect the PNS to the CNS and process some forms of sensory information and sends out responses
What are meninges?
3 layers that surround the brain and spinal cord
What does meninges do?
cushion, protect and nourish the nerve tissue
What are the 3 layers of meninges?
the dura mater, the arachnoid mater and the pia mater
What is the dura mater?
the outermost layer, made of tough fibrous connective tissue
what is the arachnoid mater?
the middle layer, net-like with vessels that reabsorb cerebrospinal fluid
What is the pia mater?
the innermost layer, very thin layer with numerous blood vessels
What is the cerebrospinal fluid and where is it found?
a clear watery fluid that is found in the central canal of the spinal cord and within the cavities of the brain
Where is the CSF made?
the choroid plexus
What is the CSF functions?
cushions and protects the brain and spinal cord from injury, supplies nutrients to nervous system issues and removes waste products from nervous system metabolism
What is the outer material of the spinal cord and what is it made of?
the white mater, it is composed of sensory nerves and motor nerves that have myelin sheaths
What is the inner material of the spinal cord and what is it composed of?
the grey mater, it is composed of interneurons that have no myelin sheaths
Where do nerve roots extend from?
the posterior and anterior horns of the spinal cord
Where do dorsal roots come from and what do they contain?
they are posterior, they are closest to the back of the body, they contain sensory neurons whose cell bodies are clumped in bulb-like regions
Where do the ventral roots come from and what do they contain?
They are anterior, they are closest to the front of the body, they contain motor neurons whose cell bodies are found in the grey matter if the spinal cord
What is the brain?
the processing center of the nervous system
What is the brain the site of?
consciousness, sensation, coordination and memory
What are the 3 regions of the brain?
the cerebrum, the cerebellum and the brain stem
What is the largest part of the brain?
the cerebrum
What does the cerebrum control?
complex mental functions like thought, reasoning, memory, and determines a persons intelligence and personality
What does the cerebrum contain?
interneurons for interpreting sensory information from sense organs initiating voluntary responses to stimuli through effectors
What are the 3 main parts of the cerebrum?
the cerebral cortex, the basal ganglia and the medullary body
What is the cerebral cortex?
the outer surface of the cerebrum which contains folds and deep grooves
How is the cerebral cortex divided?
Into the left and right hemispheres
What is the corpus callosum?
connect the left and right hemispheres with a bridge of nerve fibers
What are the 4 lobes of the brain?
the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe
What is the function of the frontal lobe?
deliberate movements, conscious thoughts, emotions
What is the function of the parietal lobe?
sensory processing, body orientation, attention
What is the function of the temporal lobe?
hearing, speech, visual and auditory memory
What is the function of the occipital lobe?
vision and object recognition
What are the specialized areas of the cerebrum?
the motor cortex, the somatosensory cortex, brocas area and wrenickes area
What is the function of the motor cortex?
controls and execution of voluntary movements