anatomy2

Chapter 7: The Nervous System


  1. Describe the structural and functional categories of the nervous system.


Structural Categories—> can be divided into TWO main structural components

  1. Central Nervous System (Brain and Spinal Cord)

  2. Peripheral Nervous System (Somatic Nervous System and Autonomic Nervous System)

  • Somatic Nervous System: Involved in voluntary control of skeletal muscles

  • Autonomic Nervous System: Controls involuntary functions such as heart rate, digestion, and breathing

Functional Categories 

  1. Afferent Division: This division carries sensory information from sensory receptors (skin, eyes, ears) to the CNS (brain). Examples—-> touch, pain, temperature, smell

  2. Efferent Division: The motor division transmits signals from the CNS (brain) to muscles and glands triggering a response. (Somatic Nervous System and Autonomic Nervous System)

  1. Distinguish between afferent and efferent neurons.


Afferent Neurons (Sensory Neurons): Nerve fibers that carry information to the Central Nervous System. Example—--> When you touch a hot surface afferent neurons in your skin detect the heat and send the signal to your spinal cord and brain


Efferent Neurons (Motor Neurons): Nerve fibers that carry impulses away from the Central Nervous System organs to the Muscles or Glands. Example—---> If your brain decides to move your hand away from a hot surface, different neurons will carry the motor command from your CNS to the muscles in your hand causing them to contract and pull your hand back.


  1. Define neuroglia. Describe the general functions of neuroglial cells.


Neuroglia (glial cells): are non-neuronal cells in the nervous system that support and maintain homeostasis, form myelin, and protect neurons.

  • Provide Support and structure.

  • Insulation

  • Protect Neurons


  1. Describe the structure and functions of neurons

Neurons=Nerve Cells specialized to transmit messages


Structures of Neurons

  1. Cell body

  2. Dendrites: tree-like extensions that emerge from the cell body, and receive electrical signals from other neurons or sensory receptors

  3. Axon: long slender extension of the neuron that carries electrical impulses away from the cell body. A myelin sheath may cover Axon. The axon transmits electrical signals from the cell body to the axon terminals.

  4. Axon Terminals: small bulbous structures at the end of the axon that make connections (synapses) with other neurons or effector cells (muscles or glands).

  5. Myelin Sheath: the fatty layer that surrounds and insulates axons and speeds nerve transmission (Schwann Cells)

  6. Node of Raviner: small gaps in the myelin sheath where the axon membrane is exposed


Functions of Neurons

  1. Sensory (afferent) neurons: carry impulses from the sensory receptors to the CNS

  2. Motor (efferent) neurons: carry impulses from the CNS to viscera and/or muscles and glands

  3. Interneurons (association neurons): cell bodies located in the CNS, that connect sensory and motor neurons


Types of Neurons 

  1. Unipolar Neurons

  2. Bipolar Neurons 

  3. Multipolar Neurons


  1. Describe the events that occur during an action potential.


The action potential is a rapid change in the membrane potential of a neuron that allows it to transmit electrical signals over long distances.

  1. Depolarization: A stimulus causes the membrane to depolarize and Sodium channels open and diffuse sodium into the neuron

  2. The peak of Action Potential: The inside of the neuron becomes very positive and sodium channels close stopping the flow of Na+

  3. Repolarization: Potassium Channels open and potassium leaves the cell making it more negative again

  1. Identify structures in a reflex arc.


5 elements of a reflex arc

  1. Sensory Receptor- reacts to a stimulus

  2. Sensory Neuron- carries message to the integration center

  3. Integration Center (CNS)- processes information and directs motor output

  4. Motor Neuron- carries a message to an effector

  5. Effector organ- is the muscle of the gland to be stimulated


  1. Distinguish between white matter and gray matter.


White Matter: composed of myelinated axons (Nerve fibers wrapped in myelin, a fatty substance). Located mostly beneath the gray matter forming the internal part of the brain. White matter is responsible for the transmission of signals between different regions of the CNS.


Gray Matter: composed of unmyelinated fibers and cell bodies and located primarily in the outer layer. Gray matter is where the processing of information occurs. It contains the cell bodies of neurons that process sensory input and execute motor commands. In the brain, gray matter is involved in higher functions such as thinking, memory, emotion, and decision-making.


  1. Describe the structure and function of the cerebral hemispheres.


Structure of the Cerebral Hemisphere

  1. The division into 2 Hemispheres: The brain is divided into two cerebral hemispheres the left hemisphere and the right hemisphere by the longitudinal fissure

  2. Outer Layer: The outer surface of each hemisphere is covered by a thin layer of gray matter called the cerebral cortex

Functions of the Cerebral Hemispheres

  1. Motor Control

  2. Sensory Processing

  3. Higher Cognitive Functions (Executive functions, Memory, Language)

  4. Perception

  5. Emotional and Social Processing

  6. Spatial Awareness


  1. Describe the structure and function of the diencephalon.


The diencephalon is a critical part of the brain located deep within the cerebral hemisphere right above the brainstem.


Structure of the Diencephalon

  1. Thalamus: Located in the center of the brain

  2. Hypothalamus: Just below the thalamus 

  3. Epithalamus: Located above the thalamus and contains the pineal gland

  4. Subthalamus


Functions of the Diencephalon

  1. Thalamus: The relay center of the brain, regulation of sleep 

  2. Hypothalamus: The control center for autonomic and hormonal functions, maintains homeostasis (body temperature, hunger, thirst, circadian rhythms, blood pressure)

  3. Epithalamus: Regulation of Biological Rhythms, The Pineal gland is involved in the regulation of circadian rhythms by secreting the hormone melatonin

  4. Subthalamus: Motor Control

  1. Describe the structure and function of the midbrain


Midbrain

  • Contains visual and auditory reflex centers

  • Contains subcortical motor centers

  • Contains nuclei for cranial nerves

  1. Describe the structure and function of the cerebellum


Cerebellum

  • Processes information from the cerebral motor cortex

  • Provides “instructions” to the cerebral motor cortex

  • Responsible for proper balance and posture


  1. Identify protective structures of the brain

  2. Describe how cerebrospinal fluid is formed and circulates


Cerebrospinal fluid is formed in the choroid plexus—-> choroid plexus capillaries found in the ventricles of the brain

  • Similar to blood plasma in composition

  • CSF forms a watery cushion to protect the brain and spinal cord

  • Circulated in the arachnoid space, ventricles, and central canal of the spinal cord

  1. Define ganglia

Ganglia: collections of cell bodies outside the CNS in the PNS

  1. Identify the function of cranial nerves


12 Pairs of nerves mostly the head and neck

  1. Olfactory- smell

  2. Optic- vision

  3. Oculomotor- six muscles that direct the eyeball

  4. Trochlear- supplies motor fibers for one external eye muscle (superior oblique)

  5. Trigeminal- chewing muscles

  6. Abducens- rolls the eye laterally

  7. Facial- facial muscles

  8. Vestibulocochlear- hearing

  9. Glossopharyngeal- swallowing, taste buds

  10. Vagus- abdominal and thoracic, digestive activity, helps regulate heart activity

  11. Accessory- activates the sternocleidomastoid, trapezius muscles

  12. Hypoglossal- control tongue movements


  1. Compare and contrast the function of the sympathetic and parasympathetic divisions of the autonomic nervous system.


Sympathetic- “fight or flight” division

  • Response to an unusual stimulus when emotionally or physically stressed or threatened

  • Takes over to increase activities

  • Remember as the “E” division (exercise, excitement, emergency, embarrassment)


Parasympathetic- “housekeeping” activities

  • Rest and Digest System

  • Conserves energy

  • Maintains daily necessary body function

  • Remember as the “D” division (digestion, Defecation, Diuresis)



Chapter 8: Special Senses


  1. Describe the function of eye accessory organs 


Eyelids

Eyelashes

Conjunctiva

Lacrimal apparatus

Extenstric Eye Muscles (6 muscles attach to the outer surface of the eye)

  • lateral rectus: moves eye laterally

  • Medial rectus: moves eye medially

  • Superior rectus: elevates eye and turns it medially

  • Inferior rectus: depresses eye and turns it medially

  • Inferior oblique: elevates eye and turns it laterally

  • Superior oblique: depresses eye and turn it laterally

  1. Describe the functions of structures in the eye


3 layers form the wall of the eyeball

  • Fibrous layer: outside layers

  • Vascular layer: middle layer

  • Sensory Layer: Inside layer


Fibrous layer

Sclera: White connective tissue layer “white of the eyes”

Cornea: transparent central anterior portion. Allows for light to pass through


Vascular Layer

Choroid: is a blood-rich nutritive layer

Ciliary body: attached to the lens by a suspensory ligament called the ciliary zonule

Iris: regulates the amount of light entering the eye

Pupil: rounded opening in the iris


Sensory Layer

Retina: contains 2 layers

  • Outer pigmented layer absorbs light and prevent it from scattering

  • Inner neural layers contains receptor cells (photoreceptors:rods and cones)


  1. Compare and contrast the different photoreceptors in the retina


Rods

  • Most are found toward the edges of the retina

  • Allow vision in dim light and peripheral vision

  • Allpereception is in gray tones

Cones

  • Allow for detailed color vision

  • Desert in the center of the retina

  • Fovea centralis- lateral to blind spot, area of the retina with only cones, sharpest vision is here

  • No photoreceptor cells are at the optic disc or blind spot


  1. Describe the different eye reflexes and how they contribute to sight 


Convergence: reflexive movement of the eyes medially when we focus on a close object

Photopupillary reflex: bright light causes pupils to constrict

Accommodation pupillary reflex: viewing close objects causes pupils to constrict


  1. Match the type of receptor with the correct sense 


Photoreceptors- vision

Equilibrium receptors: equilibrium

Maculae receptors- help keep our head erect

Olfactory receptors- smell

Gustatory cells- taste receptors

Chemoreceptors- taste and smell 


  1. Describe the location of different sensory receptors within the body.


Photoreceptors- found in the retina of the eye

Equilibrium receptors- found in inner ear specifically the vestibular system

Maculae Receptors- found in inner ear

Olfactory Receptors- found in the nasal cavity

Gustatory cells-tongue, soft palate

Chemoreceptors- located in the taste buds on the tongue and other areas of the mouth and throat