Chapter 10 Flashcards
Describe the anatomical + functional divisions of the nervous system
NERVOUS SYSTEM
1)CENTRAL NERVOUS SYSTEM
2)PERIPHERAL NERVOUS SYSTEM
divides into
-sensory/ afferent functions
-motor/efferent functions
motor functions divides into
- somatic nervous system
- autonomic nervous system
autonomic nervous system divides into
- sympathetic
- parasympathetic
Describe the CNS
- consists of the brain + spinal cord
- control center for the nervous system
- integrates all of its activities, reflexes, past happenings + current conditions to determine how it will interpret sensory input + control motor functions
Describe the PNS
- consists of peripheral nerves connecting the CNS to other parts of the body
- cranial nerves transmit impulses to + from the brain
- spinal nerves transmit impulses to + from the spinal cord
The CNS + PNS work together to do what?
provide sensory integrated + motor functions to the body
Describe the Afferent/sensory division of the PNS
- carries impulses towards the CNS from bodys sensory receptors
- somatic sensory fibers transmit impulses from the joints, skeletal muscle and skin
- visceral sensory fibers transmit impulses from the visceral organs of the ventral body cavity
- sensory division informs the CNS of all events inside + outside of the body
Describe the Efferent/motor division of the PNS
- carries impulses from the cns to effector organs
- activates muscles to contract
- activates glands to secrete
- cause motor responses
Describe the Somatic branch of the motor division
- made up of somatic motor fibers transmitting impulses from the cns to skeletal muscles
- also known as the voluntary nervous system because skeletal muscles are under conscious control
- however also controls involuntary contractions such as those involved in reflexes
Describe the Autonomic branch of the motor division
- contains visceral motor nerve fibers
- regulating glandular, cardiac muscle and smooth muscle activity
- in general, not under conscious control, involuntary nervous system
What are the two divisions of the nervous system?
CNS + PNS
What are the two divisions of the PNS?
Sensory/afferent & motor/efferent
What are the two divisions of the Motor efferent branch?
somatic and autonomic
What are the two sub-divisions of autonomic nervous system?
sympathetic and parasymmpathetic
Describe the relationship between the sympathetic and parasympathetic sub divisions
their actions usually oppose each other, when one division causes stimulation the other inhibits its actions
Name the 8 functions of the nervous system
- sensory receptors located at the ends of peripheral neurons provide the nervous systems sensory functions
- detect changes in the bodys internal + external environment + relay information. These changes may involve 02 levels, temperature, light and sound
- convents information into nerve impulses which are integrates so they can be processed to achieve the correct reaction
- motor functions act upon integrated info
- effectors cause motor responses such as muscle contractions + gland secretions
- Somatic nervous system consciously controls skeletal muscle
- Autonomic nervous system controls cardiac muscle, smooth muscle and some glands
- maintains homeostasis by responding to changes that occur
Name the structural components of a neuron
nucleus, cell body, dendrites, axon, terminal boutons
Discuss nervous tissue
consists of masses of neurons
highly cellular
neurons are structural and functional units of the nervous system
each neuron has a specalized function
how many neurons exist?
BILLIONS
How long can neurons function well for?
an entire lifetime
What do neurons require in order to function well over an entire lifetime?
adequate nutrients
Neurons are unable to divide and can not be replaces or repaired if damaged, what is this called?
Neurons are amitotic
Name the neurons that CAN be replaces
epithelium for the nose
regions of the hippocampus (memory)
Are neurons bigger than other cells?
yes
What are neurons highly specialised in?
conduction of impulses
How many axons does a neuron have?
1
Do neurons have a high or low metabolic rate?
HIGH
Due to a high metabolic rate what do neurons require continuously?
o2 and glucose
How long can a neuron survive without o2?
a few minutes
All neurons are the same shape and size, true or false?
False, they vary greatly in size and shape
Where does biosynthesis occur?
in neurons
Where are most neuron cell bodies located?
CNS
All neurons have processes that extend outwards or inwards?
outwards
What are the 2 types of processes?
dendrites and axons
The CNS contains neuron cell bodies and processes, what does the PNS contain?
mainly just processes
How many branches do dendrites have?
multiple
What is the function of dendrite branches?
act as the neurons main receptor surfaces
Describe dendrites main characteristics
tapered, short in length, diffusely branched extensions
primary receptive region of neurons
large surface area for receiving signals
How many axons do most neurons have?
1
Describe axons main characteristics
some have short axons or even lack axons
some make up almost the entire neuron length
send out electro chemical messages
Describe synaptic transmisson
- occurs in one direction
- carried by neurotransmitters (biochemicals)
- synaptic vessels release a neurotransmitter when a nerve impulse reaches the synaptic knob
- it diffuses across the cleft to react with certain receptors on the postsynaptic neuron membrane…either exciting or inhibiting a post synaptic sell
- this depends on the combined effect of excitor and inhibitory inputs from a single or too many presynaptic neurons
When do synaptic vessels release a neurotransmitter?
when a nerve impulse reaches the synaptic knob
How many directions does synaptic transmission occur in?
1
What is a synapse?
a junction between any two communicating neurons
What is the name given to the gap between two communicating neurons?
synaptic cleft
What is the function of the synaptic cleft?
to allow neurons to conduct intracellular communication across the gaps
The nervous system requires impulse transmission through neuron chains that are functionally connected by synapses. Name the 3 types of synapses
axon dendritic
axoaxonal dendriodendritic
somotodendritic
Define Axon Dentritic synapses
axon dendritic synapses are those between axon endings of one neuron + cell body of others
Which is the most common type of synapse
axon denritic
Where do axoaxonal dendriodenrtic and somotodendritic occur?
between axons, dendrites or between cell bodies and dendrites
How many axon terminals do neurons have?
1,00-10,000
Neurons have between 1,000 & 10,000 axon terminals with synapses being stimulated by an equivalent number of other …..
neurons
In what instance can post synaptic cells be other neurons of effector cells (glands and muscle)?
outside the CNS
What is a synapse between a neuron + muscle cell called?
neuro-muscular junction
Describe the job of a neuron at a neuro-glandular junction
neurons regulate or control the activities of secretory cells
What do you call a neuron carrying an impulse into a synapse?
presynaptic neuron
What name is given to the process of an impulse crossing the synaptic cleft?
synaptic transmission
What is the name of the neuron receiving the impulse?
post synaptic neuron
Most neurons can function as pre and post synaptic neurons, true or false?
true
Discuss the events that occur at a chemical synapse
- chemical synapses allow the release and reception of chemical neurotransmitters
- more common than electrical synapses
- made up of two parts, the axon terminal + neurotransmitter receptor region
- the axon terminal is a knob like structure of the presynaptic neuron
- the axon terminal contains many synaptic vesicles, which are very small membrane-bounded sacs holding thousands of neurotransmitter molecules
- the neurotransmitter receptor region is located on the postsynaptic neurons membrane
- this is usually located on the cell body of a dendrite
- the synaptic cleft is a fluid filled space that separates pre and post synaptic membranes
- clefts are approx one-millionth of an inch in width
- the electrical current from the presynaptic membrane dissipates in each synaptic cleft
- Therefore chemical synapses prevent nerve impulses from being directly transmitted between neurons
- instead they are transmitted through chemical events that are based on release, diffusion and receptor binding of neurotransmitter molecules.
- neurons therefore have undirectional communication between them
What do chemical synapses allow the release and reception of?
chemical neuro transmitters
Which are more common, chemical or electrical synapses?
chemical synapses
Chemical synapses are made up of two parts, what are they?
- axon terminal
- neurotransmitter receptor region
The axon terminal has a structure that resembles what?
a knob
Where is the neurotransmitter receptor region located?
on the postsynaptic neurons membrane
What does a synaptic cleft do?
a fluid filled space that separates pre and post synaptic membranes
What do chemical synapses prevent?
chemical synapses prevent nerve impulses from being directly transmitted between neurons
List the types of neuro transmitters
- acetylcholine
- amino acids (GABA +glutamic acid)
- monoamines (dopamine, histamine,norepine + serotonin)
- neuropeptides (endorphines, enkephalins +substance P)
- gases (nitric acid)
List the amino acids
GABA
glutamic acid
List the monoamines
- dopamine
- histamine
- norepinephrine
- serotonin
List the neuropeptides
- endorphines
- enkephalins
- susstance P
Define action potential
An action potential is the basis for a nerve impulse. It is based on the cell membrane reaching its threshold potential and is a brief reversal of membrane potential with a change in voltage of approx 100mv.
How are nerve diameters classified? (3)
- diameter
- degree of myelination
- speed of conduction
Describe group A fibres
- mostly serve the skeletal muscles, joints and skin
- primarily somatic sensory motor fibres
- they have the largest diameter of all types of fibres
- thick myelin sheaths
- fibres conduct impulses at speeds as high as 300 miles per hour
Describe group B fibres
- intermediate diameter
- light myelination
- conduct impulses at 20 mph
Describe group C fibers
- non-myelinated
- smallest diameter
- cannot create saltatory conduction
- conduct impulses at 2mph or less
Which group of fibers has the largest diameter?
group A
Which group of fibers conduct impulses the slowest?
group C
Which gorup of fibers is non-myelinated?
group C
Which group of fibers conduct impulses at 20mph?
group B
Which group of fibers conduct impulses at 2mph?
group C
Which group of fibers conduct impulses at 300 mph?
Group A
