ANS 205 Exam 2

What are the three organizations in the Nervous System?

Central, Peripheral, Autonomic

The Central Nervous System contains _______

Brain and Spinal Cord

The Peripheral Nervous System contains _______

Cranial Nerves and Spinal Nerves

The Autonomic Nervous System contains _______

Sympathetic (prepares for stress) and Parasympathetic (recovers from stress)

What are the functions of the nervous system?

- Regulate movement of body parts (locomotion)

-Regulate secretion from glands (endocrine and exocrine)

-Collect info about the external and internal environment (senses, modified neurons)

-Maintaining a state of consciousness

-Stimulate behavior for survival

T or F: All functions in the NS require rapid transmission of information

True

NS: What are the two major cell types?

Neurons and Neuroglia

Neurons

Excitable conducting cells, sensory (afferent), motor (efferent)

Neuroglia

Supporting cells, 4 types

How long is the biggest Neuron?

1.5 Ft.

NS Cells: What cells wrap around the axon and form insulating myelin sheaths?

Oligodendrocytes (CNS) & Schwann cells (PNS)

NS Cells: What cells form blood-brain barrier?

Astrocytes (CNS)

NS Cells: What cells are specialized immune cells?

Microglia (CNS)

NS Cells: What cells are one source of neural stem cells, are epithelial-like, and produce and move CSF?

Ependymal Cells

CNS: What are the three main parts of the brain?

Cerebrum, Cerebellum, Brain Stem (arranged largest to smallest)

How many parts of the brain stem are there?

4

What are the four parts of the Brain Stem?

Diencephalon (contains the epithalamus, thalamus, and hypothalamus), midbrain, pons, medulla oblongata (cell bodies involved in Autonomic NS are here)

Cerebrum

-Gyri (gyrus)- convex ridges (raised)

-Sulci (sulcus)- furrows/fissures (depressions)---Most prominent is longitudinal fissure, median plane, divides into left and right hemispheres

Gyri and Sulci define _______

Anatomical regions known as lobes

Cerebellum (dorsal)

-2 lateral hemispheres

-Median plane has a vermis (resemblance to a worm, raised ridge)

-Surface has many laminae called folia

-White matter central, Gray matter peripheral (in cerebrum and cerebellum)

-Function: Accurate timing/execution of movements and coordinate muscle activity

Brain Stem: Diencephalon

Relay center for nerve fibers connecting cerebrum to brainstem/cerebellum/spinal cord

Brain Stem: Midbrain

2 Cerebral peduncles nerves connecting spinal cord and brain stem to cerebral hemispheres and 4 colliculi containing visual reflex and nuclei for hearing

Brain Stem: Pons

Fiber tracts and cranial nerve nuclei

Brain Stem: Medulla Oblongata

Contains imp. autonomic centers and nuclei for cranial nerves

Ventricular System

A set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal and spinal cord.

-Right and left lateral ventricles (lie within cerebral hemispheres)

-Third Ventricle (located on the midline and is connected to lateral ventricle by 2 inter-ventricular foramina)

-Fourth Ventricle (connected to 3rd ventricle via aqueduct)

What is CSF?

cerebral spinal fluid- a clear fluid occupying the ventricular system and is made by ependymal cells of choroid plexus.

Spinal Cord

-Caudal continuation of medulla oblongata

-Gray matter is in the center (shaped like a butterfly)

-Spinal Cord Segment: Presence of a pair of spinal nerves formed by dorsal and ventral roots.

-Sensory (afferent) tracts

-Motor (efferent) tracts

Executes motor tracts going up and down

Axons traveling

Meninges

Connective tissue covering of brain and spinal cord (fibrous and is continuous)

-3 maters

What are the three "maters"/layers of meninges- deep to superficial?

Pia Mater

Arachnoid Mater

Dura Mater

Pia Mater

Deepest of meninges, delicate membrane that forms a sheath around blood vessels.

Arachnoid Mater

Web-like filaments

Dura mater

Tough fibrous covering (topmost layer) of CNS that allows blood to leave your brain and cerebrospinal fluid to re-enter circulation.

CSF is absorbed where?

In the sub-arachnoid space

Peripheral nervous system consists of ?

Cranial nerves and Spinal nerves

Cranial Nerves

-Carry info to and from the brain

-Are sensory, motor, or mixed

-Always 12 in number (denoted by Roman numerals)

Were once trapped, they emerged from the brain stem (for parts).

Spinal Nerves

-Carry info to and from the spinal cord

-Are mixed only (Brachial plexus, Lumbosacral plexus)

-Numbers are dependent of vertebrae

Sensory

Ascending: Taking info to brain

Motor

Descending: Taking info to structure

Autonomic NS: Sympathetic Nerves

Location of nerve beginnings: Thoracic and Lumbar

Location of junction with secondary neuron: At (or close to) sympathetic trunk.

Function: Prepare for stress

Key Neurotransmitter at organ: Catecholamines

Autonomic NS: Parasympathetic Nerves

Location of the nerve beginnings: Cranial and Sacral

Location of junction with secondary neuron: At organ

Function: Recover from stress

Key neurotransmitter at organ: Acetylcholine

What are Neurotransmitters?

Modified Amino Acids

*Acetylcholine (ACh) (neurotransmitter)

-Excitatory

-On skeletal muscles and in autonomic division of PNS and CNS

*Epinephrine/ Nor-Epinephrine

-Derived from single amino acid tyrosine (In sympathetic and asympathetic).

-Found in autonomic division of PNS

*Glutamate

-Excitatory

-Found in CNS

Helps recall, animals learn, play, fetch, etc.

*Gamma-aminobutyric acid (GABA)

-Inhibitory

-Found in CNS

*Reflex

Automatic response to a stimuli

*Reflex Arc

Entire neural circuit from stimulus detection to response (ascending & descending)

*What are the two types of reflexes?

Cranial and Spinal

*Cranial Reflexes

-Pupillary reflex

-Palpebral reflex

*Spinal Reflexes

-Withdrawal reflex

-Knee jerk reflex

Sensory System: What are the General Body Senses (somatosensation)?

-Pain, touch, temperature & proprioception

-Body surfaces & musculoskeletal elements

SS: What are the special sense organs?

-Taste (gustation)

-Smell (olfaction)

-Sight (vision)

-Hearing (audition)

-Equilibrium (vestibular sensation) ***vestibules=membranes***

Taste

Gustation

Smell

Olfaction

Sight

Vision

Hearing

Audition

Equilibrium

Vestibular Sensation-

Sensory Receptors

Specialized cells/nerve endings that detect internal or external environment (dogs barking, etc.)

Sensory Receptors: Transduction

Mechanism by which NS changes environmental energy to electrical activity of neurons.

What are the five general types of receptors?

-Mechanoreceptors: Stretch, Proprioception

-Thermoreceptors: Hot, Cold, Infrared

-Nociceptors: Dull vs. Sharp pain (nocier=pain)

-Photoreceptors: Light

-Chemoreceptors: Taste, Smell, CO2 (KTOF), pH

T or F: SS- Their receptors tend to have a structure that is specialized to detect a specific stimulus.

True

Unencapsulated Receptors

sensory dendrites that lack a connective tissue wrapping (e.g. free nerve endings and hair receptors). *free &naked*

Encapsulated Receptors

Dendrites with a glial cell wrap or connective tissue covering (e.g. Meissners corpuscles, Pacinian corpuscles in skin).

"Pain is a beautiful property". Will every animal have the same number of receptors?

No.

Pain

-Conscious perception of noxious stimuli (nocere)

-Noxious stimuli capable of causing tissue damage eg. thermal, chemical, mechanical.

Nociceptor; receptor for noxious stimuli that is a naked nerve ending (unencapsulated).

Proprioception

-Body position and movement

-Receptors in musculoskeletal system

Perception created through input of a variety of specialized receptors:

-Joint Receptors

-Muscle Spindles

-Golgi tendon organs

-Skin machanoreceptors

What four specialized receptors work together for proprioception?

-Joint Receptors

-Muscle Spindles

-Golgi tendon organs

-Skin mechanoreceptors

Gustation

-Chemical Sense

-Specialized receptors on tongue and throat

-Taste buds: Structures constituting taste cells and supporting cells.

-Taste buds confined in papillae (tiny projections)

Olfaction

-Olfactory epithelium is pseudostratified columnar

-Olfactory nerve dendrites have olfactory cilia that bind the odors to them (liquid form).

-The odor is relayed to the olfactory nerve axon which synapses dendrites of the olfactory bulb-----brain.

-Vomeronasal organ: Hard palate/nasal cavity has receptors for pheromones.

External Ear

-Pinna (locates ear at sound)

-Auditory Canal

Middle Ear

(Air-filled)

-3 ossicles: Malleus, Incus, Stapes

-Tympanic Cavity

-Auditory tube

*Continuous system that moves vibrations through ear*

Internal Ear

(Fluid-filled)

-Utricle and Saccule

-Cochlea

Hearing: Three parallel, fluid-filled channels

-Vestibular and Tympanic Duct (filled with perilymph (similar to plasma)).

-Cochlear Duct; Between Vestibular and Tympanic Duct (filled with endolymph (similar to intracellular fluid)).

-Cochlear Duct contains organ of Corti (hair cell receptors and support cells).

Vestibular Sensation

-Balance/Equilibrium

-Linear Acceleration

-Angular Acceleration

Linear Acceleration

Utriculus and Sacculus neuroepithelium with hair cells with otoliths.

-Structure: Utricle and Saccule

-Membrane: Otolithic Membrane

Angular Acceleration

Semi-circular canals (x,y,z).

Hair cells in gelatinous material

-Structure: Semicircular Canals

-Membrane: Gelatinous Membrane

Where are vibrations received and exit?

-Oval Window

Sound waves entering the ear travel through the external auditory canal, which then strikes the eardrum causing it to vibrate.

Vision: What are the three tunics of the eyeball?

-Fibrous

-Vascular

-Nerve

Fibrous (outermost)

Fibrous Tunic

-Sclera

-Cornea (transparent)

Vascular (middle)

Bloody Tunic

-Choroid (multilayered)

-Ciliary Body (vascular components & muscles)

-Iris (pigmented)

Nerve (inner)

Nervous Tunic

-Retina

*Cones & Rods (photoreceptors)

Vision

Light reflected from objects in the environment are translated into a mental image

What are the three steps of vision?

1. Light enters the eye, and the lens focuses the light on the retina.

2. Photoreceptors of the retina transduce light energy into an electrical signal (cross-section).

3. Neural pathways from retina to brain process electrical signals into visual images (On test- if you say brain stem, you're good).

What happens when light strikes rhodopsin?

It will separate into retinal and opsin which will stimulate the sodium ion channel.

What are the two types of humor?

-Aqueous Humor

-Vitreous Humor

Aqueous Humor

-Formed in posterior chamber (behind iris)

-Also in anterior chamber

-Functions: Provide nutrition to cornea and lens, remove waste products, maintain pressure.

Vitreous Humor

-Jelly-like liquid contained in body

-behind/posterior to lens

-Aqueous humor can flow into vitreous body

Adaption to Darkness

-Ratio of Cornea: Sclera

-Increased Concentration of rhodopsin

-Increased diameter of pupil

-Tapetum (lucidum): Reflective layer of inner choroid, allows light to be reflected again, eyeshine (like seeing a deer while driving).

What is the Ratio of Cornea:Sclera in cats & dogs?

-Cats: 30-90

-Dogs: 17-83

(cornea is much larger)

Endocrine System

Communication system involved in maintaining a stable internal environment (homeostasis) by enacting specific regulatory responses.

-made up of organs/ductless glands that secrete hormones to communicate with the rest of the body

What is a hormone?

-Molecules/chemical substances

-Produced by endocrine (ductless) glands

-Released into the bloodstream and carried to other parts of the body.

-Produce a specific regulatory effect

Table: Peptide Hormones

-Synthesis and Storage: Made in advance; stored in secretory vesicles.

-Location of Receptor: Cell Membrane

-Response to receptor-Ligand binding: Activation of second messenger systems; may activate genes.

-Examples: Insulin, parathyroid hormone

Table: Steroid Hormones

-Synthesis and Storage: Synthesized on demand from precursors.

-Location of Receptor: Cytoplasm or Nucleus; some have membrane receptors also.

-Response to receptor-Ligand binding: Activation of Genes for transcription and translation; may have nongenomic actions.

-Examples: Estrogen, androgens, cortisol

Table: Catecholamines

-Synthesis and Storage: Made in advance; stored in secretory vesicles.

-Location of Receptor: Cell Membrane

-Response to receptor-Ligand binding: Activation of second messenger systems.

-Examples: Epinephrine, norepinephrine, dopamine

Table: Thyroid Hormones

-Synthesis and Storage: Made in advance; pre-cursor stored in secretory vesicles.

-Location of Receptor: Nucleus

-Response to receptor-Ligand binding: Activation of Genes for transcription and translation.

-Examples: Thyroxine (T4)

Peptide Hormones

-Receptors are found in cell membrane

-Response is rapid and quickly reversed as well

-Secondary messengers: cellular components that bring about desired effects of hormone AFTER binding of hormone to receptor.

Steroid Hormones

-Receptors are found in cytoplasm/nucleus (have to get into cell itself, so their time is slower, they take longer).

-Biological responses develop slowly but last longer than peptide hormones.

-Hormone binding triggers transcription of DNA which leads to mRNA for specific proteins to be produced.

-Increase in protein production brings about desired effect of hormone.

(if in cell, it is slower)

Atypical Hormones

NOT secreted by endocrine glands

-Gastrin: Wall of stomach, stimulates release of gastric juices from gastric glands for digestion to begin.

-Secretin: Wall of SI, stimulate secretion of intestinal/pancreatic juices to continue digestion in duodenum.

-Erythropoietin: Kidney, stimulates bone marrow

Main 2 routes of hormone action

-Endocrine route (happening inside): Hormone is transported via the blood to target organ.

-Exocrine route (happening outside): Hormone is secreted to the exterior of the body where it interacts with a target organ (ex: hormones secreted into the lumen of the digestive tract).

What are the other 4 routes of hormone action?

-Paracrine route

-Autocrine route

-Neurocrine route

-Epicrine/Juxtacrine route