Part 9

HIGHER than outside.

LOWER inside the neuron, therefore HIGHER outside. Neurons are IMPERMEABLE to Na, so the cell remains polarized.

Gradients are restored by this pump. It uses ATP energy and transports 3 Na+ out for every 2 K+ it transports into the cell.

If the cell becomes sufficiently excited or depolarized (inside becomes LESS NEGATIVE), an action potential is generated. Minimum THRESHOLD membrane potential (usually around -50 mV) is level it is initiated.

When voltage-gated Na+ channels open in response to depolarization, allowing Na+ to rush down its electrochemical gradient INTO the cell, causing rapid depolarization of the segment of the cell.

Voltage gated Na+ channels then close and voltage gated K+ channels open, allowing K+ to rush OUTSIDE down its electrochemical gradient.

When a neuron shoots past the resting potential and becomes even MORE NEGATIVE than normal.

Immediately after an action potential , it my be difficult or impossible to initiate another action potential.

Sensory neurons: carry sensory info about external or internal environment TO brain and spinal cord.

MOTOR neurons: they carry them FROM the brain or spinal cord to various parts of body.

Consists of Brain and Spinal Cord.

Mass of neurons that resides in the skull. Consists of OUTER portion called GRAY matter (cell bodies) and INNER WHITE matter (mylelinated axons). Brain can be divided into FOREBRAIN, MIDBRAIN, and HINDBRAIN

Also called PROSENCEPHALON Consists of: Telencephalon and Diencephalon

• Cerebral cortex - Highly convoluted gray matter that can be seen on the surface of the brain. It processes and integrates sensory input and motor responses and is important in MEMORY and CREATIVE thought. • Olfactory Bulb - Center for reception and integration of olfactory input.

• Thalamus - RELAY and INTEGRATION center for spinal cord and cerebral cortex. • Hypothalamus - Controls VISCERAL function such as HUNGER, THIRST, SEX DRIVE, WATER balance, BLOOD pressure, and TEMPERATURE regulation. Also plays an important role in endocrine system.

RELAY center for VISUAL and AUDITORY impulses. Plas an important role in motor control. Is also called MESENCEPHALON

Also called RHOMBENCEPHALON. It is posterior part of brain. • Cerebellum - Helps modulate MOTOR impulses initiated by cerebral cortex. - important in maintenance of BALANCE, HAND-EYE coordination, and the timing of RAPID movements. • Pons - Act as a RELAY center to allow the cortex to COMMUNICATE with CEREBELLUM. • Medulla Oblangata - Controls vital functions such as BREATHING, HEART RATE, and GI activity.

Midbrain, pons and medulla oblangata

Elongated extension of the brain. OUTER WHITE matter: contains motor and sensory axons AND INNER GRAY matter containing cell bodies.

sensory info enters the spinal cord through this. The cell bodies of these sensory neurons are located in the dorsal root ganglia.

All motor information exits the spinal cord.

Flight or Fight”