A&P: the nervous system

how is the nervous system divided anatomically?

CNS: brain and spinal cord

PNS: nervous outside of the brain and spinal cord that link the CNS to various organs in the body

how is the nervou system divided functionally?

somatic nervous system: regulates activities over which there is VOLUNTARY control, such as walking, talking, and writing

autonomic nervous system: controls the body functions that occur without voluntary control, such as digestion, dilation/constriction of blood vessels, and sweating

what is the cerebrum?

largest portion of the brain [3/4], responsible for higher brain functions:

• interpreting what we see, hear, or feel

• encoding and decoding speech

• reasoning and learning

• controlling precise muscle movements

• managing emotions

split into right and left hemispheres, each of which controls the opposite side of the body

what are the 4 lobes of the cerebrum and what do they do?

• frontal: personality, judgement, planning, problem solving, concentration, and self-awareness

• parietal: recognition of spatial relationships and sensory info received from the body to form our perception of the world around us

• temporal: taste, hearing, and the ability to understand words

• occipital: vision

what is the cerebellum?

a structure that controls balance, muscle coordination, and posture

• without the cerebellum, highly specialized muscular activities like writing would be impossible

what is the brainstem?

the relay center connecting the cerebrum and cerebellum to the spinal cord → most primitive part of the CNS as it controls all involuntary, life sustaining functions [heart rate, breathing, temp regulation, digestion, vomiting, swallowing, coughing, and wake/sleep]

what are the 3 parts of the brainstem?

3 parts:

• midbrain

• pons

• medulla oblongata

what is the reticular activating system [RAS]?

a noteworthy feature within the brainstem, which is a network of neurons

• when someone gets a concussion, the immediate loss of consciousness is due to an interruption in the RAS, and the RAS has to “reboot” for the patient to regain consciousness [like a computer freezing, and the only way it can unfreeze is through a reboot]

what does the frontal lobe do?

voluntary muscle control and storage of those memories

what does the prefrontal area do?

judgement and predicting consequences of actions, and abstract intellectual functions

what does the parietal lobe do?

sense of touch and texture, and storage of those memories

what does the temporal lobe do?

hearing, smell, and language, and the storage of sound and odor memories

what does the occipital lobe do?

vision and storage of visual memories

what does the limbic system do?

basic emotions, basic reflexes [chewing and swallowing]

what does the thalamus do, and what is the other name for it?

the thalamus is also called the diencephalon [1 of 2 parts of it]

• acts as a relay center, and filters important signals from routine signals

what does the hypothalamus do, and what is the other name for it?

the hypothalamus is also called the diencephalon [1 of 2 parts of it]

what does the midbrain do?

levels of consciousness, reticular activating system, muscle tone, and posture

what does the pons do?

respiratory patterning and depth

what does the medulla oblongata do?

heart rate, blood pressure, and respiratory rate

what does the spinal cord do?

reflexes, and relays info to and from body

what are the cranial nerves?

part of the PNS

goes from brainstem to head and neck

special peripheral nerves that connect directly to body parts

what are the peripheral nerves?

part of the PNS

brain to spinal cord to body part, receives stimulus from body and sense command to the body

what does CSF do?

in addition to filtering out impurities and toxins, CSF absorbs shocks

• when significant forces are applied to the head, CSF allows the brain to shift in the skull without being damaged [some skull fracture allow CSF to leak from ears or nose]

how is blood supplied and drained from the head?

• blood is supplied to the head through the carotid artieries, which can be palpated on either side of the neck

• deoxygenated blood drains from the head via internal and external jugular veins

what is the purpose of the spinal cord?

transmit messages between the brain and the body along the nerve fibers as electrical impulses, moving quickly from one nerve to the next

where does the brainstem start and end?

spinal cord is an extension of the brainstem

foramen magnum is the opening at the base of the cranium → spinal cord travels downward within the vertebral column → cord terminates at SECOND LUMBAR VERTEBRA [L2]

how is the PNS divided?

• somatic nervous system

• autonomic nervous system

  • sympathetic and parasympathetic nervous system

what does the sympathetic nervous system do?

responsible for fight-or-flight

what does the parasympathetic nervous system do?

slow the body’s activities or returns the body to its resting state

• constriction of pupils

• promotion of digestive system activities

• constriction of airway passages

• reduction of heart rate and force of contraction

what are the sensory nerves?

complex nerves found in eyes, ears, skin, muscles, joints, lungs, and organs

• when stimulated, transmits message to the brain → detect heat/cold, relay info about position, motion, pressure, pain, balance, light, taste, smell, or some other sensation

what makes sensory nerves highly specialized?

they use specialized nerve endings unique to its type, so that it perceives and communicates info about a single type of sensation

• most sensory nerves carry info to brain via spinal cord, but some can directly take info to brain without it

  • [ex: when sensory nerves in the retina are stimulated by light, the optical nerve carries visual info from eye straight to occipital lobe of the brain]

can sensory info be acted on without the brain?

in MOST cases, sensory info cannot be acted on until the brain has received and decoded the info sent by nerves. the brain must reply with a command, which tells the body how to respond

in SOME cases, stimuli can evoke a physical response even before the message reaches the brain

what are motor nerves?

nerves that carry info from the brain to the muscles → every skeletal muscle has its own motor nerve

• motor neuron cell bodies reside in the spinal cord, and from the cell body, extend to skeletal muscles

how are signals transmitted through motor nerves from brain to body?

electrical impulse is generated by cerebral cortex → travels down nerve to muscle that neuron controls → muscle contracts