Module 6 - Nervous System Flashcards
List the 2 major divisions of the nervous system and the structures found in each.
The 2 divisions of the nervous system are the central nervous system (CNS) containing the brain and spinal cord and the peripheral nervous system (PNS) containing spinal nerves, cranial nerves, and ganglia that are outside of the PNS.
Describe the meninges and their function.
The meninges are connective tissue sheaths that surround the brain and spinal cord. The pia mater is the innermost layer of the meninges. It is thin and delicate and contains surface level blood vessels that perfuse the brain and spinal cord. The second layer of the meninges is the arachnoid layer. It encases the entire CNS and is delicate, nonvascular, and waterproof. Cerebrospinal fluid (CSF) circulates in an area just below the arachnoid layer called the subarachnoid space. The third layer of the meninges is known as the dura mater. The dura mater is a strong, continuous connective tissue sheath that provides the brain and spinal cord with most of its protection.
Brain/spinal cord - pia mater - arachnoid layer - CSF in the subarachnoid space - dura mater
Explain the divisions of the nervous system
It is divided into the CNS and PNS. The PNS is divided into the autonomic division - “involuntary”, innervate internal organs, takes care of body’s functions that happen automatically. This is divided into the sympathetic division (fight or flight, adrenaline) and the parasympathetic division (rest and relaxation; digestion and regeneration). And the Somatic division - innervates what’s voluntary like our skeletal muscles.
What are the three divisions of the brain
The hindbrain, midbrain, and forebrain.
The hindbrain consists of the cerebellum, pons, and medulla oblongata. This area is often affected by sleep disorders and CVAs. It is responsible for coordination of movement, posture, and the regulation of major body functions including respiration and blood circulation.
The midbrain includes the cerebral peduncles, bundles of nerve fibers that make up the corticospinal tracts - the main motor nerve pathway. This area of the brain regulates eye movement and is the site of visual and auditory processing.
The forebrain is the most rostral and consists of the diencephalon and cerebral hemispheres. The diencephalon consists of the thalamus and subthalamus in the dorsal horn, and the hypothalamus in the ventral horn. The cerebral hemispheres are situated around the diencephalon laterally and make up most of the brain tissue. The cerebral hemispheres can be divided into lobes: frontal, parietal, temporal, and occipital. Frontal lobe - motor cortex. Parietal - somatosensory cortex; receive sensory info. Temporal - auditory cortex. Occipital lobe - primary visual cortex.
What are the basal ganglia
masses of white matter deep in the cerebral cortex that provide the body with the ability to carry out unlearned postural movements which add to smoothness to overall mobility - swinging arm during gait.
What is the limbic system
Medial aspect of cerebrum; involved in control of emotion-related behavior
Describe how CSF is produced and its function.
CSF serves as a cushion for the brain and spinal cord protecting them from outside physical force. It maintains a constant ionic environment that allows for the diffusion of essential nutrients, electrolytes, and metabolic waste products into the extracellular fluid surrounding the CNS neurons. A thin layer of neuroglial cells, collectively known as the ependyma, line the ventricles of the brain and the central canal of the spinal cord. Specialized ependymal cells called the choroid plexus project into the ventricles and produce CSF.
List all the cranial nerves and their functions
Cranial Nerve
Function
CNI – Olfactory Nerve
Olfaction (sense of smell)
CNII – Optic Nerve
Vision (sense of sight)
CNIII – Oculomotor Nerve
Pupillary constriction, accommodation, eye movement and eye lid movement
CNIV – Trochlear Nerve
Movement of eye down and inward
CNV – Trigeminal Nerve
Mastication (chewing) and sensation to the face, nose, and mouth
CNVI – Abducens Nerve
Movement of the eye laterally
CNVII – Facial Nerve
Facial expression as well as sensation of taste to the anterior tongue
CNVIII – Vestibulocochlear Nerve
Auditory sensation (sense of hearing) as well as balance and equilibrium
CNIX - Glossopharyngeal Nerve
Motor innervation to muscles involved in swallowing as well as the sensation of taste to the posterior tongue
CNX – Vagus Nerve
Digestion, regulation of heart rate, and sensation to the digestive tract
CNXI – Accessory Nerve
Motor innervation to cervical rotator muscles and the trapezius muscle
CNXII – Hypoglossal Nerve
Voluntary tongue movements
What is the difference between afferent and efferent neurons?
Afferent neurons (sensory) bring sensory information from the spinal nerves, up through the spinal cord, to the brain for processing.
The brain sends out the efferent (motor) signal down through the spinal cord via the efferent neurons to the muscle fiber needed to enable a voluntary muscular contraction or physiologic response in the periphery.
List the neuroglial cells of the CNS and PNS.
Neuroglial cells are supportive cells that nurture and protect neurons. They can proliferate, but they cannot conduct nerve impulses or release neurotransmitters.
Ependymal cells line the ventricles or cavities in the brain and help to produce cerebrospinal fluid.
Microglial cells act as phagocytes within the CNS to clear debris, waste, or pathogens.
Oligodendrocytes produce myelin sheaths, wrappings around the neuron axons in the CNS. Myelin has a high lipid content (“white matter”), protects nueronal axons and increases overall speed of nerve impulse conduction.
Schwann cells serve the same role but for the axons in the PNS.
Astrocytes make little feet and wrap around capillaries to maintain the blood brain barrier in the brain, which helps to isolate the CNS from chemicals, toxins, pathogens, or hormones in the blood that might be detrimental to CNS tissue. They also provide structural support, help to regulate gases, and nutrient concentrations, and help to recycle or absorb neurotransmitters.
Also in the PNS are satellite cells which secrete a basement membrane protecting the cell bodies from the diffusion of larger molecules. They act to separate cell bodies and axons on the peripheral nerves from the connective tissue framework of the ganglion.
Describe 3 ways in which neurotransmitters are removed from the synaptic cleft.
A neurotransmitter can be broken down by enzymes into inactive substances.
A neurotransmitter can be drawn back into the presynaptic neuron by a process called reuptake.
A neurotransmitter can diffuse into the intercellular fluid until its concentration is too low to elicit a postsynaptic response.
Describe each phase of an action potential.
Phase 1: Resting Potential: During the resting phase, both sodium and potassium gates are closed.
Phase 2: Depolarization: The sodium gates open, and sodium rushes into the axon during the depolarization phase of the action potential. Voltage travels to zero and then up to +40 mV.
Phase 3: Repolarization: The sodium gates close, and potassium gates open allowing potassium to rush out of the axon. This returns a negative voltage to the inside of the axon.
Phase 4: After-polarization, also called hyperpolarization. Potassium gates are slow to close, and there is an undershoot of the potential. The voltage drops below -70mV and then returns to -70mV as the resting state is re-established.
Nerve signals are transmitted by action potentials (electrical impulses). They are the result of an electrochemical charge moving along an axon created by the movement of unequally distributed ions on either side of the axon’s plasma membrane. At rest, the plasma membrane is polarized (internal is negative, external is positive). The resting potential is when the axon is not conducting an impulse and this is at -70 millivots because the charge inside the axon’s cell membrane is 70 millivolts less than the outside.
The resting potential is maintained by a sodium-potassium pump, which uses active transport to carry ions across the plasma membrane - pumping three sodium ions out, 2 potassium ions in and will keep in constant motion because the Na+ and K+ ions will naturally diffuse back to where they originated. Because the plasma membrane is more permeable to K+ diffusing outward and because more NA+ ions are being pumped outward than K+ pumped inward, a relative positive charge develops and is maintained on the outside of the membrane.
If the axon is stimulated to conduct a nerve impulse, there is a rapid change in polarity. The resting potential becomes an action potential if the membrane becomes depolarized. Once an action potential occurs, it continues through the entire length of the axon, but first the membrane potential must become depolarized, indicating that the inside of the membrane is now more positive than the outside.
The action potential is due to a special protein-lined channels in the membrane, which can open to allow either Na+ or K+ ions to pass - these channels have gates. These channels and their gates are voltage activated, as proteins respond to changes in voltage with changes in shape.
What are the 5 most common neurotransmitters
Neurotransmitters are chemical messengers released from neurons via action potentials that relay a message to a post-synaptic cell. The most common are:
Acetylcholine - stimulates muscles, learning, memory
Dopamine - activates reqard mechanisms, movement, learning, attention, emotion; inhibitory
Serotonin - affects emotion, mood, hunger, perception, sleep
Glutamate - excitatory; affects learning, memory and cognition
GABA - inhibitory; affects motor control, vision, and anxiety
What are the two types of synapses
Synapses are small gaps between neurons where signals are transmitted. There are electrical synapses that allow the passage of current carrying ions through gap junctions which penetrate the cell junction of neighboring cells allowing current to flow in either direction - allows the action potential to move from one neuron to the next. Or Chemical synapses (more common) and involve a presynaptic and postsynapic neuron separated by the synaptic cleft where the presynaptic neuron sends neurotransmitters, eliciting an excitatory or inhibitory signal in one direction.
Excitatory signals depolarize the post synaptic membrane when neurotransmitters bind to the receptors producing an action potential.
What are the three EEG waves and what do they represent
Alpha wave - 8-13 Hx; person’s eyes are closed but still awake.
Beta Wave - 13-30 Hz; person is a waek with their eyes are open or are in REM sleep
Delta wave - periods of sleep; 0.5-4 Hz
