Practical 3 BSCI201

Zonules — Fibers that extend from the ciliary process and hold the lens upright.

Sphincter pupillae — Muscles that constrict the pupil for close vision and bright light.

Dilator pupillae — Muscles that dilate the pupil for distance and dim light.

Pigmented layer — Outer layer of retina containing melanocytes; absorbs light.

Neural layer — Converts light energy into nerve impulses sent to the brain.

Photoreceptors — Cells that change membrane potential in response to light.

Rods — Photoreceptors specialized for dim light; numerous in the periphery.

Cones — Photoreceptors for bright light and color; most numerous in macula lutea and fovea centralis.

Fovea centralis — Region of retina with only cones; area of highest visual acuity.

Bipolar cells — Neurons stimulated by photoreceptors; relay signals to ganglion cells.

Ganglion cells — Neurons whose axons form the optic nerve.

Optic disc (blind spot) — Region where optic nerve exits eye; contains no photoreceptors.

Anterior segment — Region between cornea and lens; contains aqueous humor.

Aqueous humor — Watery fluid in anterior segment that refracts light.

Lens — Biconvex transparent structure that refracts light.

Posterior segment — Region posterior to the lens; contains vitreous humor.

Vitreous humor — Gel-like fluid in posterior segment; maintains shape and refracts light.

Pinna — External ear structure made of elastic cartilage.

External acoustic meatus — Ear canal lined with ceruminous glands.

Tympanic membrane — Structure separating external and middle ear; vibrates with sound.

Ossicles — Three small bones of the middle ear.

Malleus — Ossicle attached to tympanic membrane and incus.

Incus — Ossicle articulating with malleus and stapes.

Stapes — Ossicle attaching to oval window; transmits vibrations to inner ear.

Pharyngotympanic tube — Connects middle ear to throat; equalizes air pressure.

Bony labyrinth — Cavities in temporal bone filled with perilymph; includes cochlea, vestibule, semicircular canals.

Perilymph — Fluid filling the bony labyrinth.

Membranous labyrinth — Soft inner passages suspended in perilymph; filled with endolymph.

What is the membranous labyrinth

Endolymph — Fluid within membranous labyrinth.

Fluid within membranous labyrinth.

Cochlear duct — Endolymph-filled duct inside cochlea.

Endolymph-filled duct inside cochlea.

Organ of Corti — Organ of hearing located within cochlear duct.

Auditory receptors (hair cells) — Receptor cells resting on basilar membrane with stereocilia in tectorial membrane.

Receptor cells resting on basilar membrane with stereocilia in tectorial membrane.

Basilar membrane — Membrane supporting hair cells; movement generates impulses.

Tectorial membrane — Membrane contacting stereocilia of hair cells.

Semicircular ducts — Endolymph-filled ducts that detect rotational movement.

Cristae ampullaris — Receptors for rotational equilibrium located in semicircular duct ampullae.

Cupula — Gel-like structure moved by endolymph to stimulate equilibrium receptors.

Saccule and Utricle — Receptors detecting linear acceleration and head position.

Chemoreceptors — Receptors for olfaction and gustation responding to chemicals in solution.

chemoreceptors

Olfactory epithelium — Organ of smell located in nasal cavity roof.

Olfactory sensory neurons — Bipolar neurons; axons form olfactory nerve; replaced every 30-60 days.

Supporting cells (olfactory) — Cells that cushion and surround olfactory neurons.

Olfactory stem cells — Stem cells replacing olfactory sensory neurons.

Taste buds — Receptor organs for taste found in papillae.

Papillae — Tongue structures where taste buds are located.

Fungiform papillae — Most numerous papillae; taste buds on superior surface.

Foliate papillae — Papillae on tongue sides; taste buds in side walls.

Vallate papillae — Large V-shaped papillae; taste buds in side walls.

Gustatory epithelial cells — Taste receptor cells within taste buds.

Microvilli (gustatory hairs) — Projections that enter taste pore and contact saliva.

Basal epithelial cells — Stem cells replacing gustatory cells every 7 days.

Sweet — Taste produced by sugars, alcohol, saccharin, some amino acids.

sweet

Sour — Taste produced by hydrogen ions (H+).

sour

Salt — Taste produced by metal ions (Na+, K+).

salt

Bitter — Taste from alkaloids such as nicotine or quinine.

bitter

Umami — Taste from glutamate or aspartate; "savory."

umami

Nervous System — Monitors and processes sensory information and body functions.

Nervous system

Central Nervous System (CNS) — Brain and spinal cord.

Peripheral Nervous System (PNS) — Cranial nerves, spinal nerves, ganglia, sensory receptors.

PNS

Neurons — Conducting cells of nervous tissue.

Neuroglia (glial cells) — Supporting cells that protect, brace, and myelinate neurons.

Glial Cells

Excitability — Ability of neurons to respond to stimuli and generate impulses.

Excitability

Conductivity — Ability to transmit impulses to other neurons, muscles, glands.

Conductivity

Amitotic — Property of neurons meaning they cannot divide.

Amitotic

Astrocytes — CNS cells that regulate chemical environment and assist capillaries.

Microglia — CNS phagocytes removing debris and pathogens.

Ependymal cells — CNS cells lining CSF cavities; circulate CSF.

Oligodendrocytes — CNS cells producing myelin.

Schwann cells — PNS cells producing myelin sheaths.

Satellite cells — PNS cells surrounding neuron cell bodies.

Cell body — Contains nucleus and cytoplasm of neuron.

Neurofibrils — Cytoskeletal fibers maintaining neuron shape.

Chromatophilic substance — Rough ER in neuron cell body.

Dendrites — Structures receiving incoming signals.

Axons — Structures transmitting impulses away from cell body.

Axon hillock — Cone-shaped region where axon originates.

Axon terminals — Store and release neurotransmitters.

Myelin sheath — Fatty insulation increasing impulse speed.

Myelin sheath gaps (Nodes of Ranvier) — Gaps aiding rapid conduction.

Multipolar neurons — Many dendrites, one axon; most common in CNS.

Bipolar neurons — One dendrite and one axon; found in sensory organs.

Unipolar neurons — One process branching into peripheral and central processes; common in PNS.

Sensory (afferent) neurons — Carry impulses toward CNS.

Sensory

Motor (efferent) neurons — Carry impulses away from CNS.

Motor

Association neurons (interneurons) — Integrate information within CNS.

Association Neurons

Tract — Bundle of CNS axons.

Tract

Nerve — Bundle of PNS axons.

Nerve

Mixed nerves — Contain both sensory and motor fibers.

Mixed nerves

Endoneurium — Connective tissue around one axon.

Endoneurium

Perineurium — Connective tissue surrounding fascicles.

perineurium

Epineurium — Connective tissue surrounding entire nerve.

epineurium

Cerebrum — Largest brain region responsible for conscious processes.

Cerebral cortex — Outer gray matter containing neuron cell bodies and dendrites.

White matter (cerebrum) — Myelinated fiber tracts under cortex.

Basal nuclei — Clusters of cell bodies deep within white matter.

Diencephalon — Thalamus, hypothalamus, epithalamus.

What is in the diencephalon

Thalamus — Relay station for sensory information except smell.

Hypothalamus — Regulates homeostasis, hormones, emotions.

Epithalamus — Contains pineal gland; secretes melatonin.

Brain stem — Midbrain, pons, medulla; controls vital functions.