EAP Ch. 8 - The Nervous System Flashcards
Fact
The nervous system and endocrine system are the two regulating systems in the body. The Central Nervous System (CNS) consists of the brain and spinal cord. The Peripheral Nervous System (PNS) consists of cranial nerves and spinal nerves. The PNS has a smaller subdivision called the Autonomic Nervous System (ANS), which is further divided into the Sympathetic Nervous System and Parasympathetic Nervous System.
Nerve Tissue
Describe: Neurons, Dendrites, Axon, Myelin sheath, Schwann Cells, Neurolemma, Gial cells, Oligodendrocytes, Microglia, Astroycyte, and Blood-brain barrier
- Nerve cells are called neurons, which are found in the CNS. Dendrites are extensions of the cell body that transmit impulses towards the cell body. Each cell has one Axon which is an extension of the cell body that transmits impulses away from the cell body.
- In the PNS axons and dendrites are wrapped in an electrically insulating myelin sheath made of Schwann Cells.The nuclei and cytoplasm of the Schwann cells are actually on the outside of the myelin sheath and are call the neurolemma - and help with regeneration.
- In the CNS myelin sheaths are formed by oligodendrocytes - no Schwann cells = no neurolemma = no regeneration.
- Glial cells = specialized cells found only in the brain and spinal cord. 1) Oligodendrocytes - myelin sheath 2) Microglia - mobile cleanup 3) Astrocyte - blood flow 4) Ependyma - circulation of cerebrospinal fluid)
- Blood-brain barrier - alcohol, nicotine, and rabies all cross. Some medications cannot.
The Nerve Impulse
Describe Saltatory conduction
Saltatory conduction: myelin sheath - only part that is visible is called the nodes of Ranvier. Only the uncovered parts get depolarized, and since there are fewer of them, it makes transmission of electrical impulses faster.
The Nerve Impulse
Describe the Squence of signal transmission, and examples of neurotransmitters
- Sequence of signal transmission: Neuron starts in polarization (not carrying an electrical pulse - cell is - inside and + outside) > Stimulus causes depolarization (cell becomes + inside and - outside) > Impulse (i.e. depolarization) continues along the neuron until it reaches the axon > Axon is triggered to emit a chemical neurotransmitter > The neuron repolarizes (i.e., resets to - inside and + outside) > The neurotransmitter emitted by the axon cross the synapse (a small gap between an axon on one neuron and a dendrite or cell body of another neuron) and either 1) triggers the dendrite (which starts the whole cycle over with depolarization of the second neuron) or 2) doesn’t trigger the dendrite (by causing hyperpolarization - how impulses are stopped)
- A nerve impulse cannot go backward across a synapse
- Examples of neurotransmitters: dopamin, serotonin, norepinephrine, etc. Each neurotransmitter has its own chemical inactivator and some neurotransmitters are simply absorbed back into the neurons that transmitted them (called reuptake)
Types of Neurons
Describe 3 types of neurons, Nerves, and Nerve tracts
- Sensory neurons carry impulses from receptors to the CNS. Can be Somatic (receptors located in skin/skeletal muscles/joints) or Visceral (receptors located in internal organs)
- Motor neurons carry impulses from the CNS to effectors (i.e. muscles and glands). Likewise, they can be Somatic (linked to skeletal muscle) or Visceral (linked to smooth muscle, cardiac muscle, and glands)
- Interneurons are found entirely within the CNS
- The PNS is made up of Sensory and Motor neurons. The Autonomic nervous system (a subsection of the PNS) is made up of the Visceral motor neurons specifically.
- Nerves (group of neurons) and Nerve Tracts (White matter in the CNS)
- Sensory nerves = sensory neurons; Motor nerves = motor neurons; Mixed nerves = both.
The Spinal Cord
Describe the anatomy of the spinal cord including: gray matter, white matter, ascending tracts, descending tracts, central canal, cerebrospinal fulid, dorsal rool and ventral root
- The Spinal Cord transmits impulses to and from the brain and is the integrating center for the spinal cord reflexes. Gray matter is the inner circle (shaped like a butterfly) and White matter is the outer circle. Gray matter has the cell bodies of motor neurons and interneurons. White matter has like invisible tracts (imagine undefined tubes running the length of the spinal cord): Ascending tracts which carry sensory impulses to the brain and Descending tracts which carry motor impulses away from the brain. The Central Canal (hole right down the middle) contains cerebrospinal fluid.
- Likewise, there are neurons coming out either side of the spinal column. The Dorsal Root carries sensory neurons into the spinal cord and the Ventral Root carries motor neurons from the gray matter out to the muscles/glands
Spinal Nerves
Describe the spinal nerves (number/names), Cauda Equina, Nerve plexus, Ganglion
- There are 31 pairs of spinal nerves (from top to bottom): Cervical (C1-C8), Thoracic (T1-T12), Lumbar (L1-L5), Sacral (S1-S5), and single Coccygeal.
- The spinal cord stops at L1 and the nerves flow out freely like a horse tail - called the Cauda Equina.
- A nerve plexus is a network of the neurons from several of segments above that combines to create nerves for specific body parts (for example, brachial plexus > radial and ulnar nerves)
- Ganglion: a group of cell bodies outside of the CNS (like little covered bundles)
Spinal Cord Reflexes
Describe Reflex, Reflex arc, Stretch reflex, and Flexor reflexes
- Reflex - an involuntary response to a stimulus
- Reflex arc (the pathway that nerve impulses travel when a reflex is elicited): Receptors (detect a change - the stimulus - and generate impulses) > Sensory neurons (transmit impulses from receptors to the CNS) > Central nervous system (contains one or more synapses - interneurons may be part of the pathway) > Motor neurons (transmit impulses from the CNS to the effector) > Effector (performs its characteristic action)
- Stretch reflex - a muscle that is stretched will automatically contract. Helps keep up upright without our having to think about doing so.
- Flexor reflexes - the stimulus is something painful and potentially harmful, and the response is to pull away from it
The Brain Parts
Describe the following brain parts: Ventricles, Medulla, Pons, Midbrain, Cerebellum, Hypothalamus, and Thalamus
- Ventricles - four cavities within the brain, filled with cerebrospinal fluid
- Medulla - bottom of the brainstem that controls vital and cardiac functions
- Pons - middle of brainstem that controls respiratory functions
- Midbrain - top of brainstem, that controls visual and auditory reflexes, and righting reflexes that keep the head upright and maintain balance or equilibrium
- Cerebellum - bottom back piece responsible for involuntary movement and certain sensory functions, muscle memory, equilibrium
- Hypothalamus - Production of ADH and oxytocin hormones, production of hormones that stimulate pituitary to release hormones, regulation of body temperature and food intake, integration of the functioning of the autonomic nervous system, stimulation of visceral response during emotional situations, regulation of body rhythms such as secretion of hormones, sleep cycles, changes in mood, or mental alertness
- Thalamus - packages multiples sensations together to send to the cerebrum
The Brain Parts
Describe the following brain parts: Cerebrum - including corpus callosum, cerebral cortex, neural plasticity, convolutions, fissures + Front lobes vs. parietal lobes vs. temporal lobes vs. occipital lobes
- Cerebrum - big main part of the brain you see (where all of the lobes are). The line separating each half has a deep groove called the corpus callosum (nerves allow side of brain to speak to each other). The cerebral cortex is the gray matter surface area (has neural plasticity - capable of being molded into new shapes), and internally is white matter. The folds are called convolutions, and the grooves between them are fissures. The folding permits the presence of millions more neurons in the cerebral cortex.
- Front lobes:
- –Motor areas that generate the impulses for voluntary movement.
- –Anterior premotor areas which are concerned with learned motor skills that require a sequence of movement (like tying shoelaces)
- – Just behind the eyes are the prefrontal areas that keep emotional responses appropriate; standard of behavior; anticipating and planning for the future; social behavior; Broca’s motor speech area, which controls the movement of the mouth involved ins peaking
- Parietal lobes: The general sensory areas receive impulses from receptors in the skin and feel and interpret the cutaneous sensations
- Temporal lobes: The olfactory areas receive impulses from receptors in the nasal cavities for the sense of smell. Auditory areas receive impulses from the receptors in the inner ear for hearing
- Occipital lobes: The visual areas receive impulses from the retinas
The Brain Parts
Describe the following brain parts: Association areas, Basal ganglia
- Association areas - parts of the cerebral cortex responsible for memories and personality; if the hippocampus is damaged, can’t form new memories or recall old ones; right hippocampus - spatial cognition; Alzhemer’s is the loss of personality due to destruction of brain neurons.
- Basal ganglia - white batter of the cerebral hemispheres, responsible for gestures and facial expression - most common disorder is Parkinson’s disease
The Brain Parts
Describe: Cerebrovasular accdents, and Aphasia (two types)
- Cerebrovascular accidents: damage to a blood vessel in the brain, resulting in lack of oxygen to that part of the brain. Types of damage: Thrombus (blood clot) blocks blood flow and aneurysm (hemorrhage) which leaks blood that puts pressure on and deprives brain tissue of oxygen
- Aphasia - when motor speech (Brocha’s) area is damaged, can still understand written and spoken words, but cannot say what they want to. Auditory aphasia (word deafness) is caused by damage to the interpretation area (can hear but not comprehend). Visual aphasia (word blindness) is when someone can see, but can’t understand written words.
Meninges and Cerebrospinal Fluid
Describe: Meninges + layers
Meninges - connective tissue membranes that cover the brain and spinal cord: thick outermost layer (dura mater) which lines the skull and vertebral canal; Middle arachnoid membrane made of web-like strand; Innermost pia mater - very thin membrane on the surface of the spinal cord and brain. Between the arachnoid and the pia mater is the subarachnoid space, which contains cerebrospinal fluid, the tissue fluid of the central nervous system. From the cranial subarachnoid space, cerebrospinal fluid is reabsorbed through arachnoid villi into the blood in cranial venous sinuses (large veins within the double-layered cranial dura mater). The cerebrospinal fluid becomes blood plasma again.
The Autonomic Nervous System
Describe: Visceral motor neurons, Autonomic pathways, Sympathetic division, and Parasympathetic division
- Part of the peripheral nervous system - specialized functions.
- Visceral motor neurons - smooth/cardiac muscle with either contract or relax and glands will increase or decrease their secretions
- 2 divisions: Sympathetic and parasympathetic that usually work opposite of each other, and are integrated by the hypothalamus.
- Autonomic pathways: Consist of two motor neurons that synapse in a ganglion outside the CNS. The first neuron is called the preganglion neuron, from the CNS to the ganglion. The second neuron is called the postganglion neuron, from the ganglion neuron to the visceral effector.
- Sympathetic division: Thoracic segments and some of the lumbar segments of the spinal cord. Brings about rapid and widespread response in many organs. Dominant in stressful situations.
- Parasympathetic division: Brainstem and the sacral segments of the spinal cord (very top and very bottom) - very localized (one organ) responses. Dominates in relaxed situations to promote normal functioning.
The Autonomic Nervous System
Describe Lumbar puncture, and Meningitis
Lumbar puncture (spinal tap): diagnostic procedure that involves the removal of cerebrospinal fluid to determine its pressure and constituents. An abnormal pressure usually indicates an obstruction in circulation, which may be caused by infection, a tumor, or mechanical injury. Meningitis caused by bacteria, fluid will be cloudy; RBCs means bleeding somewhere in the CNS.
