ANA 209 Exam 3 Study Guide Flashcards
The constituents of the central nervous system (CNS).
Brain and spinal cord.
The constituents of the peripheral nervous system (PNS).
Nerves and ganglia.
What are nerves?
Organs that contain bundles of nerve fibers (axons) that carry information to and from the CNS.
What are ganglia?
Collections of nerve cell bodies that lie outside the CNS.
Explain the PNS sensory division.
Sensory (afferent) division:
Carries signals from sensory receptors through afferent nerve fibers to the brain or spinal cord.
Visceral sensory division:
Carries signals from viscera of the thoracic and abdominal cavities.
Somatic sensory division:
Carries signals from receptors in the skin, muscles, bones, and joints.
Explain the motor division of the PNS.
Motor (efferent) division carries signals from the CNS through efferent nerve fibers to effectors (cells or organs that carry out responses).
Visceral motor division (autonomic nervous system) carries messages to glands, cardiac muscle, and smooth muscle.
Somatic nervous system send signals to skeletal muscles, many of which are under voluntary control.
What are the divisions of the autonomic nervous system?
Sympathetic: prepares body for action required in extraordinary circumstances.
Parasympathetic: Carries “business as usual” when body is in a state of rest.
What is a neuron and its properties?
Nerve cell is a neuron.
Excitability (irritability):
Neurons are highly responsive to stimuli
Conductivity:
Neurons respond to stimuli by producing electrical signals.
Secretion:
Neurons secrete neurotransmitter when an electrical signal reaches the end of the nerve fiber that passes a message to other cells.
What do sensory neurons do?
Detect stimuli and carry to brain or spinal cord.
What do interneurons do?
Lie within CNS. Receive, process, store and retrieve information. Interconnect incoming sensory pathways and outgoing motor pathways. Where decisions are made in terms of responding to stimuli.
What do motor neurons do?
Send signals to effectors (muscle and gland cells) that carry out responses.
Structure of a neuron.
Neurosoma (cell body), Nissl bodies (compartmentalized rough ER. They can synthesize proteins within the neuron), dendrites, and axons.
Parts of neurosoma.
It has a central nucleus with a prominent nucleolus. The cytoplasm contains mitochondria, lysosomes, a Golgi complex, inclusions, and an extensive rough endoplasmic reticulum and cytoskeleton. The cytoskeleton compartmentalizes the rough ER into dark-staining regions called Nissl bodies, unique to neurons.
Explain a mature neuron.
lack centrioles and do not undergo mitosis after adolescence. In recent years, researchers have discovered unspecialized stem cells in the CNS that can divide and produce new neurons.
Explain dendrites.
Dendrites are the primary site for receiving signals from other neurons. The number varies; some neurons have only one dendrite while others have thousands. The more dendrites a neuron has, the more information it can receive. The dendrites provide precise pathways for reception and processing of neural information.
Explain the axon.
Terminal arborization: Complex branches at axons distal end.
A neuron gives rise to only one axon, which arises from a mound on one side of the neuron called the axon hillock. The axon is specialized for rapid conduction of nerve signals. Axons branch at the distal end and each branch ends in a synaptic knob (terminal button). The synaptic knob forms a junction (synapse) with another cell, either another neuron, a muscle cell, or a gland cell.
What are the types of neuroglia (glial cells) and explain them?
Neuroglia, or glial cells, support neuron function.
- Oligodendrocytes. Oligodendrocytes form the myelin sheath around nerve fibers in the CNS. They have a body with as many as fifteen processes. The processes wrap around nerve fibers and insulate them from the extracellular fluid and speed up signal conduction.
- Ependymal cells. Ependymal cells resemble cuboidal epithelial cells and line the internal cavities of the brain and spinal cord. They produce cerebrospinal fluid, the liquid that bathes the CNS and fills spaces.
- Microglia. Microglia are small macrophages that derive from white blood cells. They wander through the CNS and phagocytize microorganisms, dead tissue, and foreign matter.
- Astrocytes. Astrocytes are the most abundant glial cells in the CNS. They have many branches and are somewhat star like in shape.
* Provide structural support for neurons.
* Contribute to the blood-brain barrier that controls what substances are able to get into brain tissue.
* Convert glucose to lactate and supply this to neurons for nourishment.
* Secrete factors that contribute to neuron growth and synapse formation.
* Regulate chemical composition of tissue fluid by absorbing substances such as potassium and neurotransmitters.
* Form scar tissue to fill spaces left by damaged neurons. - Schwann cells. In the PNS, Schwann cells form the myelin sheath and assist in the regeneration of damaged fibers.
- Satellite cells. Satellite cells surround the neuron cell bodies in ganglia in the PNS and regulate the chemical environment.
Separate the neuroglia into CNS and PNS
CNS glia:
Oligodendrocytes myelinate to assist conduction.
Ependymal cells secrete and circulate cerebrospinal fluid.
Microglia help in defense and disposal.
Astrocytes provide support and nourishment.
PNS glia:
Schwann cells myelinate to assist conduction.
Satellite cells provide support and nourishment.
Explain the myelin.
Myelin consists of the plasma membranes of the glial cells and is composed mostly of lipids, including phospholipids, glycolipids, and cholesterol.
Analagous (similar) to insulation on a wire.
Oligodendrocytes make fatty white matter of CNS. Each oligodendrocyte or Schwann cell wraps only part of an axon, and, therefore, each myelin sheath is segmented.
Internodes – fiber segments covered by myelin.
Nodes of Ranvier – fiber segments with gaps in myelin.
In peripheral fibers, Schwann cells surround the axon and form a sleeve called the neurilemma. External to the neurilemma there is a thin covering of fibrous connective tissue, the endoneurium. The neurilemma and endoneurium are essential for the regeneration of damaged fibers.
Nerve cells of the CNS have no neurilemma or endoneurium and are incapable of regeneration.
Explain signal conduction.
Signal conduction speed depends on two factors:
Diameter of fiber
Larger are faster.
Presence of myelin.
Myelinated are faster
Fastest fibers are both large and myelinated.
Upper and lower motor neurons; their locations and functions.
Descending tracts carry motor signals down the brainstem and spinal cord.
Upper and lower neurons involved in this.
Upper: has its soma in the cerebral cortex or brainstem
Lower motor neuron in the brainstem or spinal cord whose axon leads to a muscle or other effector.
Divisions of the spinal cord, content of the central canal of the spinal cord.
Cervical, thoracic, lumbar, sacral, and coccygeal regions.
The central gray matter in the spinal cord looks somewhat like an H or butterfly in cross-section. It consists of dorsal (posterior) horns and ventral (anterior) horns. Right and left sides are connected by the gray commissure. In the middle of the gray commissure is the central canal.
Central canal contains cerebrospinal fluid and lined with epdendymal cells.
Remember gray matter contains somas, dendrites, and proximal parts of axons. White matter consists of myelinated axons organized into bundles.
The structure of a nerve, including its three layers of connective tissue and how they relate to the organization of nerve fibers into fascicles.
Nerve is several axons wrapped by connective tissue.
Endoneurium wraps one axon. Surrounds neurilemma.
Perineurium wraps a fascicle of axons.
Epineurium wraps entire nerve. Dense irregular connective tissue.
The connective tissue layers protect the nerve from stretching and injury.
The three meninges associated with the spinal cord and their relationships.
Dura Mater: Dural sheath and epidural sheath. “Tough.” Most superficial. Protective sheath for vulnerable nervous tissue. The space between the dura mater and the bone is the epidural space, occupied by blood vessels, adipose tissue, and loose connective tissue. It is the site for epidural anesthesia.
Arachnoid mater: Spider web-like structure that adheres to the dural sheath. Arachnoid membrane is composed of simple squamous and loose mesh of collagenous and elastic fibers that span between arachnoid and the deeper pia mater.
Subarachnoid space holds Cerebral spinal fluid
and Lumbar cistern.
Pia mater: thin, translucent membrane that adheres to the spinal cord and follows its contours. Terminal filum,
Coccygeal ligament,
Denticulate ligaments.
Know which part of the nervous system controls the movement of your hand.
The median nerve (C8), radial n., ulnar n., and musculocutaneous n. of the brachial plexus.
This is part of the PNS motor division called the somatic motor division.
First- through third-order neurons.
A first-order neuron detects the stimulus and transmits the signal to the spinal cord or brainstem
second-order neuron continues to the thalamus of the brain
third-order neuron carries the signal to the sensory region of the motor cortex.
What is decussation in the ascending tracts?
The medial lemniscus pathway decussates in the medulla. (movement, fine touch, pressure, limb positions)
The spinothalamic pathways decussates in the spinal cord. (pain and temp)
You step on a sharp pin. What pathway does the pain signal follow?
The spinothalamic tract ascends in the anterior and lateral funiculi to end in the thalamus. This tract decussates in the spinal cord.
The general characteristics of a reflex.
(Brain, S.C., and peripheral)
Reflexes: Reactions to stimulation that have…
1. They are quick. They generally involve few interneurons and therefore minimal synaptic delay.
2. They are involuntary. They occur without thought in the presence of a specific stimulus.
3. The response is stereotyped; that is, it occurs in essentially the same, predictable way every time.
4. Stimulation
How visceral reflexes differ from somatic reflexes.
Visceral: responses of glands, cardiac muscle, and smooth muscle that are controlled by the autonomic nervous system.
Somatic: responses of skeletal muscles, such as occurs when you withdraw your hand from a hot stove.
- Somatic neurons system
- Rely on simple neural pathway called a reflex arc.
Components of a reflex arc.
- Somatic receptors in the skin, a muscle, or a tendon sense heat, pain, or stretch.
- Afferent nerve fibers carry information from the receptors into the dorsal horn of the spinal cord.
- An integrating center in the spinal cord or brainstem processes the information and determines whether an efferent neuron will issue a command to muscle.
- Efferent nerve fibers carry motor impulses to skeletal muscle.
- the skeletal muscles carry out a response.
In a monosynaptic reflex arc, there is no interneuron. The afferent neuron synapses directly with an efferent neuron.
Identify the location, nerves that arise from it, and structures innervated by the Cervical plexus.
NECK
1. Arises from the anterior rami of nerves C1 to C5 (neck).
- Gives rise to the lesser occipital, great auricular, transverse cervical, ansa cervicalis, supraclavicular, and phrenic nerves.
- Phrenic nerves supply the diaphragm and plays an essential role in breathing. There are motor branches that innervate the geniohyoid, thyrohyoid, scalene, levator scapulae, trapezius, and sternocleidomastoid muscles.
Identify the location, nerves that arise from it, and structures innervated by the Brachial plexus.
SHOULDER
1. Arise from the C5 to T1 nerves (C4 and T2 smaller contributions).
- Nerves that arise from the brachial plexus include musculocutaneous, axillary, radial, median, and ulnar.
- All of these nerves supply upper limb while the radial nerve supplies the muscle and skin of posterior arm and forearm and the musculocutaneous supplies the muscles of anterior arm and skin.
Identify the location, nerves that arise from it, and structures innervated by the Lumbar plexus.
LOWER BACK
1. Arise from anterior rami of nerves L1 and L4 with some fibers from T12. (lower back)
- Iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral* and obturator nerves.
- Skin of lower anterior abdominal, posterolateral gluteal regions, skin of thigh, male scrotum, root of penis, female labia, skin of knee, hip and knee joint.
FEMORAL innervates thigh skin and leg and foot and hip and knee joint as well as iliacus, pectineus, quadriceps femoris, and sartorius muscles.
Identify the location, nerves that arise from it, and structures innervated by the sacral and coccygeal plexuses.
Sacral: Below lumber
Coccygeal: Lower sacrum and coccyx
- Sacral plexus is formed from ventral rami L4, L5, and S1 and S4. Coccygeal lexus is formed from ventral rami of S4, S5, and Co1.
- The sacral plexus gives off the sciatic nerve which is a combo of tibial and common fibular nerves (SCIATIC nerve) The coccygeal plexus gives rise to anococcygeal nerve.
- Sciatic nerve focuses on injury and pain.
The location, anatomical features, and functions of the medulla oblongata.
Location:
Begins at foramen magnum (of skull) -> ending at a transverse groove marking the boundary between medulla and pons.
Features:
- Contains nerve fibers that travel between brain and S.C.
- 4 pairs of cranial nerves begin or end at nuclei in the medulla
- Contains cardiac center, vasomotor center, respiratory center
Functions:
- regulates rate and force of heartbeat
- blood pressure and flow by dilating/constricting blood vessels
- rate and depth of breathing and speech, coughing, sneezing, salivation, swallowing, gagging, vomiting, and sweating
The location, anatomical features, and functions of the pons.
Location:
- Section of brainstem between the midbrain and medulla
Features:
- 2 pairs of thick stalks called cerebellar penduncles (connect pons and midbrain)
- Two spinal cord sensory tracts: anterolateral system and anterior spinocerebellar tract
- Cranial nerves V-VIII
- White matter in anterior half
Functions:
- Hearing, equilibrium, taste, facial sensations (touch and pain), eye movement, facial expressions, chewing, swallowing, secretion of saliva and tears
The location, anatomical features, and functions of the midbrain.
Location:
- Part of brainstem between pons and diencephalon
- Connects hindbrain and forebrain
Features:
- central gray substance
- tectum (4 bulges)
- tegmentum (main mass and has red nucleus)
- SUBSTANTIA NIGRA (dark gray to black nucleus from melanin, motor center that relays inhibitory signals to the thalamus and basal nuclei, degeneration of this leads to muscle tremors of parkinsons)
Functions:
- motor movement, visual reflexes, superior colliculus for visual attention and inferior colliculus for auditory attention.
Limbic system and its functions.
A ring of brain structures that encircles the corpus and thalamus, cingulate gyrus(arches over corpus callosum), hippocampus, amygdala, and other structures
Functions:
- Learning, emotion, memory, gratification, aversions (fear, pleasure, sorrow)
The location and general organization of the hypothalamus and its functions.
Forms the walls and floor of the 3rd ventricle and gives rise to the posterior pituitary gland
- Hormone secretion (growth, metabolism, reproduction, and stress)
- Autonomic effects (heart rate, blood pressure, pupillary diameter, gastrointestinal secretion and motility)
- Thermoregulation
- Food and water intake (hunger and satiety)
- Sleep and circadian rhythm
- Emotional and sexual responses
- Memory
Functions:
- Relays signals from the limbic system to the thalamus, control center of autonomic nervous system and endocrine system, appetite, thirst, body temperature
- Maintaining homeostasis
The cerebral locations of primary and association cortex for each of the special senses: vision, hearing, equilibrium, taste, and smell .
Vision:
- Occipital lobe
- Primary visual cortex
Hearing:
- Temporal lobe and insula
- Primary auditory cortex
Equilibrium:
- Cerebellum
- Several brainstem nuclei
Taste:
- Parietal lobe
- Primary gustatory cortex
Smell:
- Temporal and frontal lobes
- Orbitofrontal cortex.
The somatosensory organization of the postcentral gyrus and its location.
The thalamus routes all somesthetic/ general signals to the postcentral gyrus of the parietal lobe.
Lies caudal to the central sulcus and forms the anterior borer of the parietal lobe. Rises from lateral sulcus up to the crown of the head and then descends into the longitudinal cerebral fissure.
Where is Wernicke’s area in the cerebrum and what is its function?
Posterior to lateral sulcus of left brain, usually in left hemisphere.
Recognition of written and spoken language.
Formulates phrases and transmits a plan of speech to the Broca area.
Where is Broca’s area in the cerebrum and what is its function?
Inferior prefrontal cortex of left brain (same hemisphere as wernickes).
Speech.
Generates a motor program for the muscles of the larynx, tongue, cheeks, and lips to produce speech.
Transmits to the primary motor cortex, which executes it.
Location and functions of corpus callosum.
The corpus callosum connects the two hemispheres so both sides of the brain can communicate with each other.
Seen superior to the third ventricle in a median section of the brain.
Location and functions of thalamus.
Located inferior to the corpus callosum and bulging into each lateral ventricle.
The thalamus is a large ovoid mass that makes up 4/5ths of the diencephalon. Called the gateway to cerebral cortex. Involved in sensation, movement, memory, and emotion. It is the relay station of sensory signals to the cerebrum.
Synaptic relay of nearly all signals passing from lower levels of the CNS to cerebrum.
What contributes to the blood-brain barrier?
A barrier between the bloodstream and nervous tissue of the brain that is impermeable to many blood solutes and thus prevents them from affecting the brain tissue; formed by the tight junctions between capillary endothelial cells, the basement membrane of the endothelium, and the perivascular feet of astrocytes.
BBB is only permeable to water, glucose, and lipid-soluble substances.
Brain is only 2% of body weight but receives 15% of blood and uses 20% of oxygen and glucose
Blood–brain barrier (BBB)
- Seals capillaries in brain tissue
- Tight junctions between endothelial cells
Blood–CSF barrier
- Seals choroid plexus within brain ventricles
- Tight junctions between ependymal cells
Circumventricular organs (CVO)
- Regions of 3rd and 4th ventricles that lack BBB
- Allow brain to monitor blood chemistry
The two-neuron pathway of autonomic output.
Preganglionic fiber
- Neurosoma in brainstem/spinal cord
- Axon extends to an autonomic ganglion somewhere outside the CNS
- Meets the neurosoma of the second neuron and secretes ACh
- Myelinated
Postganglionic fiber
- Neurosome in the ganglion
- Axon from second neuron
- Leaves ganglion and extends to the target or or cell
- Secretes ACh or norepinephrine
- Excitatory or inhibitory
- Unmyelinated
Which nerve endings is found in the skin?
The muscles for your eyes movements. Upward, downward.
Upward- superior rectus & inferior oblique
Downward- inferior rectus & superior oblique
Lateral and medial rectus
What is the structure of rods and cone cells?
Rods- night vision with the pigment rhodopsin. The rods have an outer segment that has a stack of membranous discs enclosed in a plasma membrane. Each disk is studded with the pigment rhodopsin.
Cones- highly concentrated in the fovea. Day vision and fine-resolution detailed images. The outer segment tapers to a point and the discs are parallel infolding not separate discs.
Describe the anatomy of the cochlea.
The spiral organ has epithelium composed of hair cells and supporting cells. The hair cells are so named because of stiff microvilli on their surface called stereocilia. Resting on top of the stereocilia is the tectorial membrane. Hair cells are not neurons but they synapse with nerve fibers at their base.
What are the semicircular ducts in the ear?
A ring-shaped, fluid-filled tube of the inner ear that detects angular acceleration of the head; enclosed in a bony passage called the semicircular canal. There are three semicircular ducts in each ear.
Lateral, anterior, posterior
The semicircular ducts are filled with endolymph. Each duct opens into the utricle and has a dilated sac at one end called an ampulla. Within the ampulla are hair and supporting cells. A gelatinous membrane called a cupola extends to the roof of the ampulla. When the body accelerates, the duct rotates but the endolymph lags behind and pushes the cupola. This bends the stereocilia on the cupola and stimulates hair cells. This is how semicircular ducts detect acceleration.
How different regions of the retina differ in function.
The retina contains rods, cones, bipolar cells, and ganglion cells. The conversion of light energy to action potentials occurs in the retina.
The most posterior layer, the pigment epithelium, consists of darkly pigmented epithelial cells who basal processes interdigitate with receptor cells of the retina. It absorbs light and prevents it from degrading the visual image.
The neural part of the retina consists of three cell layers; from back to front there are photoreceptors, bipolar cells, and ganglion cells. Photoreceptor cells are the rods and cones. Rods and cones synapse with dendrites of bipolar cells (1st order neurons in visual pathway). Second order neurons are called the ganglion cells (detect light intensity) and their axons converge to form the optic nerve.
Label the spinal cord regions
Label the parts of the spinal nerve
Label the rami
Label the phrenic nerve
Label the parts of the brainstem
Label the ventricles
Label the CN V Trigeminal Nerve
Label the CN VII Facial Nerve
Label the parts of the ear
Label the parts of vision
