Study Guide: Nervous and Endocrine Systems, Special Senses (Lab Practical Exam 3)

Nervous System

Overview of the Nervous System

The nervous system is responsible for coordinating the body's responses to internal and external stimuli. It is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).

• CNS: Consists of the brain and spinal cord; processes and integrates information.

• PNS: Composed of nerves and ganglia outside the CNS; transmits signals between the CNS and the rest of the body.

Nerve vs. Tract

• Nerve: A bundle of axons in the PNS.

• Tract: A bundle of axons in the CNS.

• Example: The optic nerve (PNS) vs. the optic tract (CNS).

Structural Classifications of Neurons

Neurons are classified based on the number of processes extending from the cell body.

Classification	Location where this classification can be found
Multipolar	Most common; CNS (brain and spinal cord)
Bipolar	Special senses (retina of eye, olfactory epithelium)
Unipolar (Pseudounipolar)	Sensory neurons in PNS (dorsal root ganglia)

Neuron Structure and Synapse

• Presynaptic cell: The neuron sending the signal.

• Postsynaptic cell: The neuron or effector cell receiving the signal.

• Synapse: The junction where information is transmitted from one neuron to another.

Afferent vs. Efferent Neurons

• Afferent (Sensory) neurons: Carry impulses from sensory receptors toward the CNS.

• Efferent (Motor) neurons: Carry impulses away from the CNS to effectors (muscles/glands).

Parts of a Nerve

• Endoneurium: Surrounds individual axons.

• Perineurium: Surrounds bundles of axons (fascicles).

• Epineurium: Surrounds the entire nerve.

• Blood vessels: Supply nutrients to the nerve.

Major Regions of the Brain

• Cerebrum

• Diencephalon

• Brainstem

• Cerebellum

Lobes and Structures of the Brain

• Frontal lobe: Voluntary movement, planning, reasoning.

• Parietal lobe: Sensory processing.

• Temporal lobe: Auditory processing, memory.

• Occipital lobe: Visual processing.

• Central sulcus: Separates frontal and parietal lobes.

• Lateral sulcus: Separates temporal lobe from frontal/parietal lobes.

• Precentral gyrus: Primary motor cortex.

• Postcentral gyrus: Primary somatosensory cortex.

Cranial Nerves

There are 12 pairs of cranial nerves, each with specific modalities and functions.

Roman numeral	Name	Modality	Function
I	Olfactory	Sensory	Smell
II	Optic	Sensory	Vision
III	Oculomotor	Motor	Eye movement, pupil constriction
IV	Trochlear	Motor	Eye movement (superior oblique)
V	Trigeminal	Both	Facial sensation, chewing
VI	Abducens	Motor	Eye movement (lateral rectus)
VII	Facial	Both	Facial expression, taste (anterior 2/3 tongue)
VIII	Vestibulocochlear	Sensory	Hearing, balance
IX	Glossopharyngeal	Both	Taste (posterior 1/3 tongue), swallowing
X	Vagus	Both	Autonomic control of viscera
XI	Accessory	Motor	Shoulder and neck muscles
XII	Hypoglossal	Motor	Tongue movement

Protection of the Brain

• Four protective structures: Skull, meninges, cerebrospinal fluid (CSF), blood-brain barrier.

• Meninges (outermost to innermost):

  1. Dura mater

  2. Arachnoid mater

  3. Pia mater

Brainstem and Diencephalon

• Brainstem: Midbrain, pons, medulla oblongata; controls basic life functions.

• Diencephalon: Thalamus (sensory relay), hypothalamus (homeostasis), epithalamus (pineal gland).

Special Senses

Ear Structure

• Outer ear: Auricle, external auditory canal, tympanic membrane.

• Middle ear: Ossicles (malleus, incus, stapes), auditory tube.

• Inner ear: Cochlea (hearing), vestibule and semicircular canals (balance).

Eye Structure

• Fibrous layer: Sclera, cornea.

• Vascular layer (uvea): Choroid, ciliary body, iris.

• Neural layer: Retina (photoreceptors: rods and cones).

• Tapetum lucidum: Reflective layer in some animals (e.g., cows) to enhance night vision.

Muscles of the Eye and Their Actions

Muscle	Action
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
Superior oblique	Depresses eye and turns it laterally
Inferior oblique	Elevates eye and turns it laterally

Retina and Photoreceptors

• Rods: Detect dim light, black and white vision.

• Cones: Detect color and detail, concentrated in the fovea centralis.

Endocrine System

Major Endocrine Glands

Endocrine Gland	Location	Hormone Released
Pituitary (anterior/posterior)	Base of brain	Growth hormone, ADH, etc.
Pineal	Brain (epithalamus)	Melatonin
Thyroid	Neck, below larynx	Thyroxine (T4), triiodothyronine (T3)
Parathyroid	Posterior thyroid	Parathyroid hormone (PTH)
Adrenal (cortex/medulla)	Above kidneys	Cortisol, epinephrine
Pancreas	Behind stomach	Insulin, glucagon
Ovary (female)	Pelvic cavity	Estrogen, progesterone
Testis (male)	Scrotum	Testosterone

Thyroid Hormones and Regulation

• Hormones produced: Thyroxine (T4), triiodothyronine (T3), calcitonin.

• Regulation: Thyroid hormones are regulated by TSH (thyroid-stimulating hormone) from the anterior pituitary.

• Hyperthyroidism: Excess thyroid hormone; symptoms include weight loss, increased metabolism.

• Hypothyroidism: Deficient thyroid hormone; symptoms include weight gain, fatigue.

• Thyroid removal or destruction: Results in hypothyroidism; requires hormone replacement therapy.

Feedback Mechanisms

• Negative feedback loop: Hormone secretion is inhibited by the hormone's own effects (e.g., high T3/T4 inhibits TSH release).

• Positive feedback loop: Hormone secretion is stimulated by the hormone's effects (less common; e.g., oxytocin during childbirth).

Additional info:

• Some tables and diagrams were inferred and expanded for clarity.

• All major topics correspond to chapters on the nervous system, special senses, and endocrine system.