• Nerve impulses have a domino effect. Each neuron receives an impulse and must pass it on to the next neuron and make sure the correct impulse continues on its path. Through a chain of chemical events, the dendrites (part of a neuron) pick up an impulse thats shuttled through the axon and transmitted to the next neuron. The entire impulse passes through a neuron in about seven milliseconds — faster than a lightning strike. steps
Heres what happens in just six easy steps• Polarization of the neurons membrane: Sodium is on the outside, and potassium is on the inside.• Resting potential gives the neuron a break.• Action potential: Sodium ions move inside the membrane.
• Repolarization: Potassium ions move outside, and sodium ions stay inside the membrane.• Hyperpolarization: More potassium ions are on the outside than there are sodium ions on the inside.• Refractory period puts everything back to normal: Potassium returns inside, sodium returns outside.
SYNAPSES The coordination of cellular activities in animals is usually considered to involve• an endocrine system: where the response is to hormones: chemicals secreted into the blood by endocrine glands and carried by the blood to the responding cell.• a nervous system: response to electrical impulses passing from the central nervous system to muscles and glands.
SYNAPSE CONSIST• a presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles• a postsynaptic ending that contains receptor sites for neurotransmitters• a synaptic cleft or space between the presynaptic and postsynaptic endings.
TYPES OF SYNAPSES• Axodendritic Synapse• Axosomatic Synapse• Axoaxonic Synapse
SENSORY RECEPTORS• a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. In response to stimuli the sensory receptor initiates sensory transduction by creating graded potentials or action potentials in the same cell or in an adjacent one.
FUNCTIONS• RECEPTION, which is the ability of a cell to absorb stimuli of energy• TRANSDUCTION is the conversion of stimulus energy into a change in membrane potential of a receptor cell• AMPLIFICATION is responsible for strengthening stimulus energy, and can occur in either accessory structures, or as a part of transduction.• TRANSMISSION which conducts impulses to the central nervous system• INTEGRATION is the process of information and begins as soon as information starts to be received
EXTEROCEPTORS• Neurological receptors that receive information from the environment external to the organism.
INTERORECEPTORS• Neurological receptors that receives information from the internal environment• Examples blood pressure, pH and O2 of the blood, body temperature, blood glucose and GIT distension