Biología. Tema 1

The peripheral nervous system (PNS) is composed of all the nerves that extend from the brain and spinal cord to the rest of the body.

Cranial nerves are 12 pairs of nerves that originate from the brainstem and control sensory and motor functions of the head and neck.

Spinal nerves are 31 pairs of nerves that originate from the spinal cord and control sensory and motor functions of the body.

Afferent nerves carry sensory information from the body to the central nervous system (CNS).

Efferent nerves carry motor commands from the CNS to the body.

The somatic nervous system controls voluntary muscle movements.

The autonomic nervous system controls involuntary bodily functions, like breathing, heart rate, and digestion.

The sympathetic nervous system prepares the body for 'fight or flight' responses to stressful situations.

The parasympathetic nervous system promotes relaxation and energy conservation, returning the body to its resting state.

The sympathetic nervous system releases the neurotransmitter norepinephrine, which triggers the 'fight or flight' response.

The parasympathetic nervous system releases the neurotransmitter acetylcholine.

The sympathetic system increases heart rate and blood flow to muscles during stress.

The parasympathetic system slows heart rate and promotes digestion.

Preganglionic neurons are neurons with their cell bodies in the CNS, and their axons project to the autonomic ganglia.

Postganglionic neurons are neurons with their cell bodies in the autonomic ganglia, and their axons project to target organs.

The somatic nervous system has a direct connection between the CNS and skeletal muscles.

The autonomic nervous system has a two-neuron pathway – preganglionic and postganglionic neurons.

Sympathetic preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord.

Parasympathetic preganglionic neurons originate in the brainstem and sacral regions of the spinal cord.

The sympathetic nervous system dilates the pupils.

The parasympathetic nervous system constricts the pupils.

Sympathetic nerve stimulation increases the heart rate.

Parasympathetic nerve stimulation decreases the heart rate.

The sympathetic nervous system stimulates the release of sweat.

The parasympathetic nervous system stimulates digestion by increasing activity in the digestive system.

The parasympathetic nervous system stimulates the release of saliva.