Exam 2 Flashcards
(117 cards)
1
Q
Sensory nerve only
Associated with sense of smell
Bipolar neurons; pass through cribriform plate of ethmoid bone, and enter olfactory bulbs
A
Olfactory nerve I (1)
2
Q
Sensory nerve only
Associated with sense of vision
Neuron cell bodies form ganglion layers of retina, and pass through optic foramina of the orbits.
A
Optic nerve II (2)
3
Q
Primary motor nerve
Monitor impulses to several voluntary muscles that rise eyelids, & move the eye
Motor impulses to involuntary muscles that focus the lens, & adjust the light entering your eye (Part of autonomic nervous system)
Small sensory component (Proprioceptive fibers)
A
Oculomotor nerve III (3)
4
Q
Primary motor nerve
Smallest pair of cranial nerves
Motor impulses to one pair of muscles that move the eyes
Small sensory component (Proprioceptive fibers)
A
Trochlear nerve IV (4)
5
Q
Mixed nerve
Largest part of sensory branches
3 large sensory branches:
1. Opthalmic division: Sensory from surface of eyes, tear glands, scalp, forhead, & upper eyelids
2. Maxillary division: Sensory from upper teeth, upper gum, upper lip, palate, & skin on the face
3. Mandibular division: Sensory from scalp, skin of jaw, lower teeth, lower gums, lower lip, & muscles of mastication (Chewing)
A
Trigeminal nerve V (5)
6
Q
Primary motor nerve
Motor impulses to one pair of muscles that move the eyes
Some sensory (Proprioceptive fibers)
A
Abducens nerve VI (6)
7
Q
Mixed nerve
Special sensory from taste receptors
Somatic motor to muscles of facial expression
Autonomic motor to tear glands, & salivary glands
A
Facial nerve VII (7)
8
Q
Sensory nerve only
Acoustic or auditory nerve
2 branches:
* Vestibular branch: Sensory form equilibrium receptors of the ear
* Cochlear branch: Sensory from hearing receptors
A
Vestibulocochlear nerve VIII (8)
9
Q
Mixed nerve
Sensory from pharynx, tonsils, part of tongue (posterior third), carotid arteries
Motor to salivary glands (autonomic) & muscles o pharynx (for swallowing, somatic)
A
Glossopharyngeal nerve IX (9)
10
Q
Mixed nerve
Somatic motor to muscles of speech & swallowing
Autonomic motor to heart, & other viscera of the thorax & abdomen
Sensory from pharynx, larynx, esophagus, & viscera of thorax & abdomen
A
Vagus nerve X (10)
11
Q
Primary motor nerve
Aka “Spinal accessory”
Contain crainal & spinal branches
* Cranial branch: Motor to muscles of soft palate, pharynx, & larynx ; Join Vagus N
* Spinal branch: Motor to muscles of neck & back ; Small sensory component (proprioceptive fibers)
A
Accessory nerve XI (11)
12
Q
Primary motor
Motor to muscles of tongue
Small sensory component (Proprioceptive fibers)
A
Hypoglossal nerve XII (12)
13
Q
Conducts impulses into brain or spinal cord
A
Sensory Nerves
14
Q
Conducts impulses to muscle or glands
A
Motor Nerves
15
Q
Contain both sensory & motor nerve fibers
Contains all spinal nerves (except the first pair) & most nerves
A
Mixed Nerves
16
Q
T/F: Nerves are bundles of axons
A
True
17
Q
What are the 3 connective tissue coverings located on the structures of periphreal nerves?
A
Endoeurium: Around each axon (Outside Myelin Sheath)
Perineurium: Around fascicles (Bundle of axons)
Epineurium: Around whole nerve
18
Q
12 pairs total on underside of brain
* 4 are mixed
* 3 are sensory
* 5 are primary motor, innervate muscles or glands
Most are attached to brainstem w/ 2 exceptions
* First pair has fibers that start in nasal cavity & send impulses directly to cerebral cortex
* Second pair originates in eyes, & fiber synapse in thalamus
Anterior & posterior pairs associated w/ cerebrum
Superior & inferior pairs associated w/ remaining
A
Cranial Nerves
19
Q
What are the 4 major parts of the brain?
A
Cerebrum
Dienecphalon
Cerebellum
Brainstem
20
Q
what are the 3 ventricles in the brain?
A
Forebrain (Prosencephalon): Divides brain into telenecephalon & diencephalon
Midbrain (Mesencephalon)
Hindbrain (Rhombencephalon): Divides into metencephalon & myelencephalon
21
Q
What 3 structures make up the brainstem?
A
Midbrain
Pons
Medulla Oblongata
22
Q
What are the 5 lobes in the Cerebrum?
A
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Insula (Island of Reil)
23
Q
Association areas Carry on higher intellectual process for:
* Concentrating
* Planning
* Complex problem solving
* Emotional behavior, jusging consequences of behavior
Motor areas control movements of voluntary skeletal muscles
A
Frontal lobe
24
Q
Sensory areas are responsible for hearing & interpret complex sensory experiences (understanding speech, & reading)
* Auditory
Associated areas interpret sensory experiences & remember visual scense, music, & other complex sensory patterns
A
Temporal lobe
25
**Sensory** areas provide sensations of temperature, touch, pressure, & pain involving the skin
Association areas function in understanding speech & using words to express thoughts & feelings
Part of lobe associated w/:
* Understanding speech
* Choosing words to express thoughts & feelings
Parietal lobe
26
Sensory areas are responsible for vision
Association areas combine **visual** images w/ other sensory experiences
Part of lobe associated w/ *analyzing & combining viual images w/ other sensory experiences*
Occipital lobe
27
Translating sensory information into proper emotional response
Insula
28
What is the difference between a Dominant Hemisphere & a Nondominant Hemisphere?
**Dominant Hemisphere:**
* Language skills of speech, writing, & reading
* Verbal, analytical, & computational skills
**Nondominant Hemisphere:**
* Nonverbal tasks
* Motor tasks
* Understanding & interpreting musical & visual patterns
* Provides emotional & intuitive thought process
29
What are 5 neuron structures?
**Dendrites**: Receive signals
**Cell body**: Manufacture cell components, & intergrate signal
**Axon**: Conduct impulses
**Synaptic Knob**: Site of contract w/ target cell
**Myelin Sheath**: Formed by neuroglia cells to insulate axons ; Interrruped in Periheral neurons by nodes
30
99% of neurons
Many processes
Most neurons of CNS
*3+ processes*
Multipolar neurons
31
What is the difference between a Bipolar Neuron & an Unipolar neuron?
**Bipolar Neuron:**
* 2 processes
* Eyes, ears, nose *(special senses)*
**Unipolar neuron:**
* 1 process
* Cell bodies are in ganglia
* *Sensory neuron*
* Dendrites fuse w/ Axons
* *Special senses *
32
**Afferent neurons**
Carry impulses to CNS
Most are **unipolar**
Some are bipolar
Sensory Neurons
33
Association Neurons
**Link sensory & motor neurons**
Multipolar
Located in CNS
Interneurons
34
**Multipolar, efferent**
Carry impulses away from CNS
Carry impulses to effectors
Motor Neurons
35
**Connect neurons to blood vessel**
* Exchange nutrients & growth factors
**Acts as filter for brain**
Form scar tissue
Aid metabolism of certain substances
**Regulates K+**
Part of Blood Brain Barrier
**Astrocytes** (Neuroglia of CNS)
36
**Myelinated CNS axons**
Provies structural support
**Oligodenroctyes** (Neuroglia of CNS)
37
Phagocytic cell
Provides structural support
**Microglia** (Neuroglia of CNS)
38
**Line central canal to spinal cord & ventricles of brain**
* *Cover choroid plexuses*
Help regulate composition & circulation of cerebrospinal fluid
Cuboidal or columnar cells; ciliated
**Ependyma / Ependymal cells** (Neuroglia of CNS)
39
**PNS neuroglia that encase axons in a sheath**
Speed up speed of nerve impulse transmission
Wrap tightly around axon in layers **composed of myelin** *(Lipoprotein mixtures)*
* *Coating called Myelin Sheath*
**Node of Ranvier:** Gaps in Myelin Sheath between Schwann cells
Schwann Cells
40
Support clusters of neuron cell bodies (ganglia)
Protect cell body
**Satellite cells** (Neuroglia of CNS)
41
If peripheral axon is injured, it may regenerate
Axon separated from cell body and its myelin sheath will degenerate
Schwann cells and neurilemma remain
Remaining Schwann cells provide guiding sheath for growing axon
If growing axon establishes former connection, function will return; if not, function may be lost.
Neuron Regeneration in the *PNS*
42
CNS axons lack neurilemma to act as guiding sheath.
Oligodendrocytes do not proliferate after injury.
Regeneration is unlikely
Neuron Regeneration in the*CNS*
43
Propagated down the length of the axon as *nerve impulses*
***Axon hillock / Initial segment / Trigger zone* at first part of axon contains many voltage-gated sodium channels**
When **threshold is reached (-55 mV), voltage-gated *Na+ channels open*** (Beginning of the action potential)
***Na+* ions diffuse into the cell, and membrane *depolarizes (Toward 0)***
Na+ channels close and K+ channels open
**K+ diffuses out of the cell, and membrane *repolarizes (Toward -70)***
The **voltage goes a below -70 mV**, so the membrane is **temporarily *hyperpolarized (-90)***
Then K+ channels close
Na+/K+ pumps bring the membrane back to **RMP (-70 mV)**
Action Potentials
44
Transmission of a nerve impulse from one neuron to another
* **Connection between nerves**
**Connect dendrite of 1 neuron to axon of another**
Neurotransmitters are released when impulse reaches *synaptic knob*
*2 types of potentials:*
* **Excitatory postsynaptic potential** *(EPSP)*
* **Inhibitory postsynaptic potential** *(IPSP)*
* *EPSPs and IPSPs are added together* in a process called **summation**
Synapse
45
Membrane change in which neurotransmitter opens Na+ Channels
Depolarizes membrane of postsynaptic neuron, as Na+ enter axon
Action potential in postsynaptic neuron becomes *more* likely
Excitatory **postsynaptic potential** (EPSP)
46
Membrane change in which neurotransmitter opens K+ channels (or Cl- channels)
Hyperpolarizes membrane of postsynaptic neuron, as K+ leaves axon
Action potential of postsynaptic neuron becomes *less* likely
Inhibitory **postsynaptic potential** (IPSP)
47
Decisions are acted upon
Impulses are carried to effectors (muscles or glands)
Divisions of motor portion of PNS
**Somatic Nervous System:** transmits voluntary instructions to skeletal muscles
**Autonomic Nervous System:** transmits involuntary instructions from the CNS to smooth muscles, cardiac muscle, and glands
Motor Function of the nervous system
48
*PNS* have a series of Schwann cells lined up along the axon, each having a wrapped coating of myelin insulating the axon
Myelinated axons
49
Encased by Schwann cell cytoplasm, but there is no wrapped coating of myelin surrounding the axons.
Unmyelinated axons
50
During an impulse, the portion of the axon actively conducting the action potential is not able to respond to another threshold stimulus of normal strength
Limits number of action potentials generated per second
**Longest is cardiac ; Shortest is skeletal**
**2 Parts:**
* Absolute Refractory Period
* Relative Refractory Period
Refactory Period
51
What are 3 factors affect impulse conduction?
**Increase in concentration of K+ in extracellular fluid:**
* Increase in concentration of K+ to leave cell; threshold potential reached with stimulus of lower intensity; leads to excitable neurons, perhaps convulsions
**Decrease in concentration of K+ in extracellular fluid:**
* Neurons can become hyperpolarized; action potentials are not generated; lack of impulses leads to muscle paralysis
**Decrease in permeability to K+ ions:**
* Can be caused by some anesthetic drugs; stops impulses from passing through tissue fluid around axon; impulses do not reach brain, and there is no perception of touch and pain
52
Where are neurotransmitters produced?
Rough ER or cytoplasm
53
Neurotransmitters are released by ____________.
A) Endocytosis
B) Exocytosis
B) Exocytosis
54
Consists of the brain & spinal cord
* Brain is the largest & most complex part of the nervous system
* Brain controls sensation, perception, movement, & thinking
Central Nervous System (CNS)
55
Membranes that protect brain & spinal cord
Consists of 3 layers:
* *Dura mater* (Outer layer)
* *Arachnoid mater* (middle layer ; weblike)
* *Pia mater* (Inner layer attached to spinal cord)
Meningies
56
Outer layer of meningies
Tough, dense connective tissue
Dural sinuses
Epidural space
Dura Mater
57
Middle layer ; web-like
Subarachnoid space contains cerebrospinal fluid (CSF)
Arachnoid mater
58
Inner layer ; attached to surface of brain & spinal cord
Blood vessels & nerves
Nourishes CNS
Pia mater
59
*Cushions brain*
**Secreted by the choroid plexuses**, special capillaries of pia mater covered by ependymal cells
**Stored in arachnoid space**
Selective transfer of substances from the blood to form
* Nutritive & protective
After exchange substances are **absorbed by the arachnoid granulations**
Cerebrospinal fluid (CSF)
60
**Continuous secretions & reabsorption of cerebrospinal fluid (CSF) keeps fluid pressure in ventricles constant**
Interference w/ circulation of CSF (by infection, tumor, blood clot) can increase ICP in ventricles
**Can lead to collapse of cerebral blood vessels, injury to brain tissue (Compressed against skull)**
**Pressure can be relieved by inserting a drain into subarachnoid space**
* *Ex: hydrocephalus in an infant can be treated w/ a shunt*
Cerebrospinal Fluid Pressure
61
Neural centers for sensory function
Sensations & perceptions
Motor commands to skeletal muscles
Higher mental functions (memory, reasoning)
Neural centers for regulating visceral activities
Personality
Brain
62
What is the larges part of the brain?
A) Cerebrum
B) Cerebellum
C) Thalamus
D) Corpus callosum
A) Cerebrum
63
Thin layer of **gray matter**
Makes up outermost layer of the cerebrum
Interpretes impules from sensory organs
* Creating sensations
* Forming perceptions
Initiating voluntary movements
Storing information as memory
* Retrieving stored info
Reasoning, seat of intelligence & personality
Cerebral Cortex
64
**Lies deep to the cerebral cortex**
Makes up most of cerebrum
Contains bundles of myelinated axons
**White matter** of cerebrum
65
What are the 6 *sensory areas* of the cortex?
**Cutaneous Sensory Area:**
* Parietal Lobe
* Interprets sensations on skin
**Sensory Speech Area (*Wernicke's Area*):**
* Temporal / parietal lobe
* Usually left hemisphere
* Understanding & formulating language
**Visual Area:**
* Occipital Lobe
* Interprets vision
**Auditory Area:**
* Temporal lobe
* Interprets hearing
**Sensory Area for Taste:**
* Near base of the central sulcus
* Includes part of insula
**Sensory Area for Smell:**
* Arise from centers on the deep side of temporal lobes
66
What are the *motor areas* of the cortex?
**Primary motor areas:**
* Frontal lobes
* Control voluntary muscles
* Most nerve fibers cross over in brainstem
**Brocas area:**
* Anterior to primary motor cortex
* Usually in left hemisphere
* Controls muscles needed for speech
**Frontal eye field:**
* Above Brocas area
* Controls voluntary movements of eyes & eyelids
67
*Between cerebral hemispheres & above the brainstem*
*Surrounds the 3rd ventricle*
**Composed of gray matter**
Contains:
* **Thalamus / Hypothalamus**
* Posterior pituitary
* Pineal gland
Diencephalon
68
Gateway for sensory impulses ascending to cerebral cortex
Receives all sensory impulse (except for sense of smell)
Thalamus
69
Maintain homeostasis by regulating visceral activities:
* HR, BP, temp
* Water, electrolytes
* Hunger, body weight, movement
* Glandular secretions (digestive tract)
* Pituitary gland function
* Sleep & wakefulness
Links nervous & endocrine systems
Hypothlamus
70
Consists of several structures in various parts o brain, including diencephalon
Controls emotions response, feelings, & behaviors oriented toward survival
Reacts to potentially life-threatening upsets (Physical or psychological)
Limbic System
71
Lies between diencephalon & pons
Contains bundles of fibers that join lower parts of brainstem & spinal cord w/ higher part of the brain
Cerebral aqueduct
Midbrain
72
Rounded bulge on underside of brainstem
* Between midbrain & medulla oblongata
Relays nerve impulses between medulla oblongata & cerebrum
Relays impulses from cerebrum to cerebellum
Helps regulate rhythm of breathing
Pons
73
Enlarged continuation of spinal cord
**Conducts ascending & descending impulses between brain & spinal cord**
**Contains cardiac, vasomotor, & respiratory control centers**
Contains various nonvital reflex control centers (Coughing, sneezing, swallowing, & vomiting)
Injuries are fatal
Medulla Oblongata
74
**Inferior to occpitial lobes ; Dorsal to pons & medulla oblongata ; posterior to brain**
*Cerebellar cortex (Gray matter)*
**Arbor Vitae (White mater)**
**Integrates sensory information concerning position of body parts**
**Coordinates skeletal muscle activity, maintains posture**
Cerebellum
75
**Slender column of nerve tissue continous w/ brain & brainstem**
**Extends downward through vertebral canal**
*Begins at the foramen magnum & terminates at first & second lumbar vertebrae* (L1, L2) space
31 segments, each give rise to a pair of nerves
Grouped according to the level of vertebra w/ which they are associated
Spinal cord
76
What are the *Longitudinal sections* of the spinal cord?
Cervical enlargment
Lumbar enlargement
Conus medullaris
Filum terminale
Cauda equina
77
What is the diference between ascending & descending tracts?
**Ascending Tracts:** Conduct sensory impulses to the brain (pink)
* *Sensory neurons*
**Sescending Tracts:** Conduct motor impulses from the brain via **motor neurons** reaching muscles & glands (light brown)
*Tracts are composed of axons (white matter)*
78
Consists of nerves that connect CNS to other body parts
Includes:
* **Cranial Nerves**: Arising from the brain
* **Spinal Nerves:**Arising from the spinal cord
Divided into 2 parts:
* **Somatic Nervous System:** Cranial & spinal nerves that connect CNS to the skill & skeletal muscles (Consciois activites)
* **Autonomic Nervous System:** Cranial & spinal nerves that connect CNS to viscera (Subconscious activities)
Peripheral Nervous System
79
There are 31 pairs of spinal nerves. How many are in the following:
_ Cranial nerves (C _ to C _ )
_ Thoracic nerves (T _ to T _ )
_ Lumbar nerves (L _ to L _ )
_ Sacral nerves (S _ to S _ )
_ Coccygeal nerves (C _ )
**8** Cranial nerves **(C1 to C8)**
**12** Thoracic nerves **(T1 to T12)**
**5** Lumbar nerves **(L1 to L5)**
**5** Sacral nerves **(S1 to S5 )**
**1** Coccygeal nerves **(C0 )**
80
Whats the difference between Anterior (ventral) Root & Posterior (dorsal) root
**Anterior (ventral) Root:** *Motor root*
* Cell bodies found in gray matter of spinal cord
**Posterior (dorsal) root:** *Sensory root*
* Posterior root ganglion: Contains cell bodies of sensory neurons
81
What are the 4 branches of spinal nerves outside the spinal cord?
Meningeal branch
Posterior branch/ramus
Anterior branch/ramus
Visceral branch (only in thoracic & lumbar)
82
*Complex network formed by anterior rami (branches) of spinal nerves*
*Not in T2-T12, instead anterior rami become intercostal nerves*
Fibers of various spinal nerves are sorted & recombined, so all fibers heading to same peripheral body part reach in the same nerve
**3 Nerve Plexuses:** Cervival, brachial, lumbosacral
Nerve Plexus
83
**Formed by anterior rami (branches) of C1-C4 spinal nerves**
Lies deep in the neck
Supply muscles & skin of the neck
*C3-C5 nerve roots contribute to* **phrenic nerves**, which transmt motor impulses to the diaphragm
Cervical Plexus
84
Formed by anterior branches C5-T1
Lies deep w/in shoulders
5 branches:
* **Musculocutaneous Nerve:** Supply muscles of anterior arms & skin of forearms
* **Ulnar & Median Nerve:** Supply muscles of forearms & hands, skin of hands
* **Radial Nerve:** Supply posterior muscles of arm & skin of forearms & hands
* **Axillary Nerve:** Supply muscles & skin of anterior, lateral, & posterior arms
Brachial Plexus
85
**Formed by the anterior branches of L1-S4 roots**
Lumbar portions are in lumbar regions of the abdomen, & the sacral portions are in pelvic cavity
**Obturator Nerve:** Supply motor impulses to adductors of thighs
**Femoral Nerve:** Supply motor impulses to muscls of anterior thigh & sensory impulses from skin of thighs & legs
**Sciatic Nerve:** Supply muscles & skin of thighs, legs & feet; largest/longest nerve in body
Lumbosacral Plexus
86
Part of PNS
Functions w/o conscious effort
Controls visceral activities
**Regulates smooth muscle, cardiac muscle, & glands**
**Helps maintain homeostasis & helps body respond to stress**
Prepares body for exercise, intense physical activity
Autonomic Nervous System (ANS)
87
What are 2 divisions of Autonomic Nervous System (ANS)?
**Sympathetic Division:**
* Prepares body for "fight or flight" situations ; speeds body up
* Most active under energy-requiring, stressful, emergency situations
**Parasympathetic Division:**
* Prepares body for "resting & digesting" activities ; slows body down
* Most active under resting, nonstressful conditions
88
Autonomic motor pathway contains what 2 neurons?
**Preganglionic Fibers:**
* Axons of preganglionic neurons
* Neuron cell bodies are in CNS
**Postganglionic Fibers:**
* Axons of postganglionic neurons
* Neuron cell bodies in ganglia
* Extend to visceral effector
* Ectends sympathetic ganglia to visceral effector organs
89
Thoracolumbar division (T1-L2)
Preganglionic fibers originate in spinal cord, leave via ventral roots & enter **sympathetic chain (paracertebral) ganglia**
* Send distance from viscera (regulate)
Sympathetic chain ganglia + fibers that connect them make up **sympathetic trunk**
*Ex: Collateral ganglia in abdomen lie close to some large blood vessels*
Sympathetic Division
90
What are 2 types of autoniomic neurotransmitters?
**Cholinergic Neurons:**
* Releases acetylcholine
* Postganglionic parasympathetic fibers
**Adrenergic neurons:**
* Release Norepinephrine (noradrenaline)
* Most postganslionic sympathetic fibers
91
Collect information for the enviornment, & relay it to the CNS on sensory neurons
Link to nevous system to internal & external changes/events
Can be specialized cells or multicellular structures
Sensory receptors
92
What are the 5 sensoy receptors in the body?
**Chemoeceptors:** Respond to changes in chemical concentations
* Smell, taste, O2 concentration
**Pain Receptors:** Responds to tissue damage
* Mechanical, electrical, thermal energy
**Thermoreceptors:** Respond to modeate changes in temp
**Mechanoreceptors:** Respond to mechanical foces that distort receptor
* Touch, tension, BP, stretch
**Photoreceptors:** Respond to light
* Eyes
93
What are the 3 goups of general senses?
**Exteroceptive senses:** Exteroceptive senses
**Interoceptive (visceroceptive) senses:** Senses associated with changes in the viscera, such as blood pressure stretching blood vessels
**Proprioceptive senses:** Senses associated with changes in muscles, tendons, and joints, as when changing position or exercising
94
What are 3 pain-inhibiting substances produced in the body?
Enkephalins
Serotonin
Endorphin
95
Have receptors in internal organs
Convey information that includes the sense of fullness after eating a meal as well as the discomfort of intestinal gas and the pain that signals a heart attack
**Examples of visceral receptors:** lamellated corpuscles, free nerve endings.
Visceral senses
96
Once olfactory receptors are stimulated, nerve impulses travel through openings in cribriform plates of ethmoid bone *(bipolar neuron)*
*Olfactory receptor cells → olfactory bulbs → olfactory tracts → limbic system (for emotions) and olfactory cortex (for interpretation).*
Limbic system, center for memory and emotion, provides emotional responses to certain odorant molecule
Olfactory Pathways
97
Sensory impulses from taste receptor cells travel on fibers of 3 different cranial nerves, according to the location of the taste cells:
* **Facial nerve (VII)**
* **Glossopharyngeal nerve (IX)**
* **Vagus nerve (X)**
Cranial nerves conduct impulses into medulla oblongata
Impulses then proceed to the thalamus.
Impulses are interpreted in the gustatory cortex in the insula
Taste Pathways
98
What are the accessory organs for sense of sight?
Upper and lower eyelids (*palpebrae*, protection)
Eyelashes (protection)
Lacrimal apparatus (tear production)
Extrinsic eye muscles (eye movement)
99
Composed of 4 layers:
* Skin
* Muscle
* Connective tissue
* Conjunctiva
**Orbicularis oculi** muscle closes eyelid
**Levator palpebrae superioris** muscle opens eyelid
**Tarsal glands** secrete oil onto eyelashes
Eyelids **(Palpebrae)**
100
Cornea + Sclera
**Cornea:**
* Anterior sixth.
* Transparent.
* Helps focus light rays.
* Transmits and refracts light
**Sclera:**
* Posterior five sixths.
* White, opaque.
* Protects eye, attaches muscles.
* Pierced by optic nerve and blood vessels
Outer (fibrous) tunic
101
**Forms internal ring around the front of the eye**
Processes are the radiating folds.
Muscles contract and relax to move lens
* Changes lens shape for focusing
Suspensory ligaments hold lens in position
Anterior portion / Thickest portion
Pigmented.
Ciliary body
102
Controls amount of light entering the eye controlling the size of the pupil (hole in the iris).
* located in front of lens.
Consists of connective tissue and smooth muscle (colored portion of eye).
Anterior to ciliary body.
Pigmented.
Iris
103
Window or opening in center of iris.
*Dim light stimulates radial muscles and causes dilation*
*Bright light stimulates circular muscles and causes constriction*
Amount and distribution of melanin determines eye color
Pupil
104
**Consists of retina**
* *Retina contains visual receptors (photoreceptors)*
Continuous with optic nerve in back of eye & ends just behind margin of the ciliary body toward front of eye
Composed of several layers.
* **Macula lutea:** yellowish spot in retina.
* **Fovea centralis:** center of macula lutea; produces sharpest vision.
* **Optic disc:** blind spot; contains no photoreceptors; found where nerve fibers from retina leave eye to become optic nerve.
* **Vitreous humor:** thick gel that holds retina flat against choroid coat, and helps maintain the eye’s shape.
Inner (Nervous) Tunic
105
What ae the 3 layes of the eye?
**Outer layer:**
* *Posteior porition:* Sclera
* *Function:* Protecion
* *Anterior portion:* Cornea
* *Function:* Light transmission & refaction
**Middle layer:**
* *Posteior porition:* Choroid coat
* *Function:* Blood supply, pigment prevents reflection
* *Anterior portion:* Ciliary body, iris
* *Function:* Accomidation, contols light intensity
**Inner layer:**
* *Posteior porition:* Retina
* *Function:* Photoreception, impulse conduction
106
Long, thin projections.
*Contain light sensitive pigment, called rhodopsin*
Hundreds of times more sensitive to light than cones.
**Provide vision in dim light**
**Produce vision without color in shades of gray**
*Produce outlines of objects*
Named for shape of receptive ends: *Cylindrical*
Rods
107
Short, blunt projections
*Contain light sensitive pigments, called erythrolabe, chlorolabe, and cyanolabe*
**Provide vision in bright light**
*Produce sharp images*
**Produce color vision**
*Fovea centralis contains only cones*
Named for shape of receptive ends: *conical*
Cones
108
*Light-sensitive pigment in rods*
In presence of light, decomposes into Opsin and Retinal
**Triggers a complex series of reactions that initiates nerve impulses**
*Impulses travel along optic nerve*
Rhodopsin (Visual purple)
109
Each type of cone contains different light-sensitive pigment.
Each type of cone is sensitive to different wavelengths.
Color perceived depends on which types of cones are stimulated.
**Erythrolabe:** responds to red light.
**Chlorolabe:** responds to green light.
**Cyanolabe:** responds to blue light.
Iodopsins (pigments in cones)
110
Abundant in hairless portions of skin & lips
Detect fine touch & texture
Distinguish between 2 points
*Type of mechanoreceptor associated w/ touch & pressure senses*
Tactile (**Meissner's**) Corpuscles
111
Nerve endings encased in lage ellipsoidal structures
Common in deeper subcutaneous tissues, tendons and ligaments.
Detect heavy pressure and vibrations.
*Type of mechanoreceptor associated w/ touch & pressure senses*
Touch & pressure senses
112
Consist of free nerve endings
Widely distributed.
Nervous tissue of brain lacks pain receptors.
Stimulated by tissue damage, chemicals, mechanical forces, or extremes in temperature.
Adapt very little, if at all.
Pain receptors/nociceptors
113
Visceral pain may feel as if coming from some other part of the body
Results from common nerve pathways, in which sensory impulses from the visceral organ and a certain area of the skin synapse with the same neuron in the CNS.
**Example of referred pain:** Heart pain often feels like it is coming from the left shoulder or medial portion of left arm.
Reffered pain
114
Senses that have sensory receptors are within large, complex sensory organs in the head
**Smell:** olfactory organs in nasal cavity.
**Taste:** taste buds in oral cavity.
**Hearing and equilibrium:** inner ears.
**Sight:** eyes
Special senses
115
What are the 5 primary taste sensations?
**Sweet:** stimulated by carbohydrates.
**Sour:** stimulated by acids (H+)
**Salty:** stimulated by salts (Na+ or K+)
**Bitter:** stimulated by many organic compounds, M g and C a salts.
**Umami:** stimulated by some amino acids, MSG.
116
What are the 3 parts of the outer ear?
**Auricle (Pinna):**
* Funnel-shaped
* Collects sounds waves
**External acoustic meatus:**
* S-shaped tube.
* Lined with ceruminous glands.
* Carries sound to tympanic membrane.
* Terminates at tympanic membrane
**Tympanic membrane (Eardrum):**
* Vibrates in response to sound waves
117
What are the 5 parts of the middle ear?
**Tympanic cavity:**
* Air-filled space in temporal bone
**Auditory ossicles:**
* 3 tiny bones.
* Vibrate in response to tympanic membrane vibrations; amplify force.
* Malleus, incus and stapes.
* Hammer, anvil and stirrup
**Oval window:**
* Opening in wall of tympanic cavity.
* Stapes vibrates against it to move fluids in inner ear.
**Tympanic Reflex:**
* Muscle contractions that occur during loud sounds, to lessen the transfer of sound vibrations to inner ear, and prevent damage to hearing receptors.
* Muscles involved are *tensor tympani and stapedius*
**Auditory (eustachian) tube:**
* Connects middle ear to throat.
* Helps maintain equal pressure on both sides of tympanic membrane.
* Usually closed by valve-like flaps in throat.
