Nervous system Lecture 9&10 Flashcards
divisions of the nervous system
central,
peripheral, autonomic, somatic, visceral, sympathetic,
parasympathetic
central nervous system
brain and spinal cord
peripheral nervous system
nervous tissue outside the CNS
special sensory receptors
monitor smell, taste, vision, balance and hearing
visceral sensory receptors
monitor internal organs
somatic sensory receptors
monitor skeletal muscles, joints and skin surface
somatic nervous system
skeletal muscles
spinal cord
- The spinal cord is enclosed in the vertebral column and runs from foramen magnum of the skull to the level of L1 or L2
- Provides communication to and from brain
- Like the brain, protected by bone, meninges and cerebrospinal fluid
- 31 pairs of spinal nerve roots issue from the spinal cord
- Enlarged in cervical and lumbosacral regions, where the nerves serving the upper and lower limbs arise
where does the spinal cord run from
The spinal cord is enclosed in the vertebral column and runs from foramen magnum of the skull to the level of L1 or L2
Cauda equina
during development, vertebral column grows faster than spinal cord, so lower spinal nerves ‘chase’ their exit points inferiorly
spinal nerves
31 pairs of paired spinal nerves arise from the spinal cord
there can be 8 cervical nerves but only 7 cervical vertebrae
first 7 spinal nerves arise superior to the vertebrae for which they are named, spinal nerve 8 arises inferior to the 7th cervical vertebra
how many spinal nerves arise from the spinal cord
31
somatic spinal nerve
each spinal nerve attaches to the spinal cord via dorsal and ventral root
these unite to form a spinal nerve before emerging from intervertebral foramina
spinal nerves are short (1-2cm); almost immediately after emerging from foramen, they divide into a dorsal (posterior) ramus and a ventral (anterior) ramus and a tiny meningeal ramus that innervate meninges and blood vessels
dorsal roots
contain sensory (afferent) fibres
ventral roots
contain motor (efferent) fibres
pattern of somatic sensory innervation of the skin
the area of skin innervated by a single spinal nerve is called a dermatome
hilton’s law: any nerve serving a muscle that produces a movement at a joint also innervates the joint and the skin over the joint
BRACHIAL PLEXUS
nerves to the arm • Musculocutaneous • Median – muscles of the underside of the forearm, including wrist flexors and flexors of the thumb and first 2 fingers • Ulnar – muscles of the underside of the forearm, plus flexors of digit 4 and 5 • Radial – muscles on the back of the forearm, which extend to the wrist and all fingers • Axillary
autonomic nervous system
regulates glands, smooth muscle and cardiac muscle
uses two-neuron chain
-preganglionic neuron
-postganglionic neuron
SYMPATHETIC
PARASYMPATHETIC
preganglionic neuron
ANS
from brain or spinal cord to autonomic ganglion outside CNS
postganglionic neuron
ANS
from ganglion to effector organ
sympathetic ns
expends energy (catabolic) or stimulates spinal nerves T1-L2
parasympathetic ns
conserves energy (anabolic) or calms CN 3, 7, 9, 10 and S2-4
anabolic
conserves energy
anabolic substances tend to promote cell growth
catabolic
expends energy
catabolic substances promote energy release
parasympathetic division
• Anatomically simpler
• Also called craniosacral division as fibres
originate at opposite ends of CNS
• Eye, salivary glands, heart, lungs, stomach, pancreas, liver and gall-bladder served by cranial outflow
• Bladder and genitals served by sacral outflow
• Ganglia close to target organs
• Postganglionic fibres shorter than preganglionic fibres
sympathetic division
- More complex; innervates more organs
- Arise from T1 to L2
- Ganglia close to spinal cord
- Postganglionic fibres longer than preganglionic fibres
major divisions of the brain
forebrain
midbrain
hindbrain
frontal lobe
thinking, memory, behaviour and movement
temporal lobe
hearing, learning and feelings
parietal lobe
language and touch
OCCIPITAL lobe
sight
cerebellum
balance and coordination
brainstem
breathing, heart rate and temperature
meninges
dura mater arachnoid pia mater functions: - Cover and protect CNS - Protect blood vessels - Contain cerebrospinal fluid - Form partitions in the skull Meninges cover and protect the spinal cord as well.
When does human life begin?
There are 7 scientific views.
metabolic view genetic embryological immunological ecological/technological neurological integrated psychological
pregnancy
from fertilisation to birth
gestation
from last menstruation to birth
embryo
from fertilisation to week 8
foetus
= from week 9 to birth
infant
from birth
pregnancy week 1
Fertilisation,
morula,
blastocyte,
implantation
pregnancy week 2
Bilaminar embryo,
placenta and membranes,
gastrulation
pregnancy week 3
Gastrulation (germ layers),
neurulation (neural tube),
early circulatory system
pregnancy week 4
Protoheart beats,
branchial arches,
limb buds
pregnancy week 5-8
Organogenesis
, face, limb differentiation,
external genitalia
pregnancy week 9-38
Brain growth,
neural connections,
size growth
fertilisation
Oocyte and sperm fuse to form the zygote, this is fertilisation.
• Oocytes are viable for 12-24h after leaving the ovary
• Sperm is able to fertilise the oocyte for 24-48h after ejaculation
• So, coitus has to occur between 2 days prior ovulation to 1 day after for fertilisation to be successful
• Sperm capacitation = newly ejaculated sperm cannot penetrate the oocyte; they need to be capacitated. Sperm mobility is enhanced and membrane broken down, it is achieved by female reproductive tract
first week of embryo development
morula and blastocyte
At the start of this week, you ovulate. Your egg is fertilized 12 to 24 hours later if a sperm penetrates it – and this simple biological occurrence begins a series of increasingly complicated processes that leads to a new human life, if all goes well. Over the next several days, the fertilized egg will start dividing into multiple cells as it travels down the fallopian tube, enters your uterus. In the uterus, the cells continue to divide, becoming a hollow ball of cells called a blastocyst. The blastocyst implants in the wall of the uterus about 6 days after fertilization.
SECOND WEEK OF EMBRYONIC
DEVELOPMENT
bilaminar embryo forms
the epiblast and the hypoblast are sandwiched between two balloons: the primitive yolk sac and the amniotic cavity
THIRD WEEK OF EMBRYONIC DEVELOPMENT
trilaminar embryo
ectoderm (epidermis and cns),
mesoderm (musculoskeletal; cardiovascular and urogenital systems)
and endoderm (lining of gastrointestinal tract)
WEEK 3 and 4 of embryonic development
neurulation (brain and spinal cord)
notochord forms from mesoderm cells
signals from notochord cause inward folding of ectoderm at the neural plate
ends of neural plate fuse and disconnect to form an autonomous neural tube
the notochord
- Defines the body’s axis
- Provides support
- Basis of axial skeleton (bones of head and vertebral column)
- Indicates future site of vertebral bodies
- Mesodermal cells immediately below the primitive streak aggregate, forming a rod of mesodermal cells called the notochord
- Eventually disappears as vertebrae bodies form, but persists as nucleus pulposus of each vertebral disc
